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## A Simple Stochastic Climate Model: Climate Sensitivity

Last time I derived the following ODE for temperature T at time t:



where S and τ are constants, and F(t) is the net radiative forcing at time t. Eventually I will discuss each of these terms in detail; this post will focus on S.

At equilibrium, when dT/dt = 0, the ODE necessitates T(t) = S F(t). A physical interpretation for S becomes apparent: it measures the equilibrium change in temperature per unit forcing, also known as climate sensitivity.

A great deal of research has been conducted with the aim of quantifying climate sensitivity, through paleoclimate analyses, modelling experiments, and instrumental data. Overall, these assessments show that climate sensitivity is on the order of 3 K per doubling of CO2 (divide by 5.35 ln 2 W/m2 to convert to warming per unit forcing).

The IPCC AR4 report (note that AR5 was not yet published at the time of my calculations) compared many different probability distribution functions (PDFs) of climate sensitivity, shown below. They follow the same general shape of a shifted distribution with a long tail to the right, and average 5-95% confidence intervals of around 1.5 to 7 K per doubling of CO2.

Box 10.2, Figure 1 of the IPCC AR4 WG1: Probability distribution functions of climate sensitivity (a), 5-95% confidence intervals (b).

These PDFs generally consist of discrete data points that are not publicly available. Consequently, sampling from any existing PDF would be difficult. Instead, I chose to create my own PDF of climate sensitivity, modelled as a log-normal distribution (e raised to the power of a normal distribution) with the same shape and bounds as the existing datasets.

The challenge was to find values for μ and σ, the mean and standard deviation of the corresponding normal distribution, such that for any z sampled from the log-normal distribution,





Since erf, the error function, cannot be evaluated analytically, this two-parameter problem must be solved numerically. I built a simple particle swarm optimizer to find the solution, which consistently yielded results of μ = 1.1757, σ = 0.4683.

The upper tail of a log-normal distribution is unbounded, so I truncated the distribution at 10 K, consistent with existing PDFs (see figure above). At the beginning of each simulation, climate sensitivity in my model is sampled from this distribution and held fixed for the entire run. A histogram of 106 sampled points, shown below, has the desired characteristics.

Histogram of 106 points sampled from the log-normal distribution used for climate sensitivity in the model.

Note that in order to be used in the ODE, the sampled points must then be converted to units of Km2/W (warming per unit forcing) by dividing by 5.35 ln 2 W/m2, the forcing from doubled CO2.

## Climate Change and Atlantic Circulation

Today my very first scientific publication is appearing in Geophysical Research Letters. During my summer at UVic, I helped out with a model intercomparison project regarding the effect of climate change on Atlantic circulation, and was listed as a coauthor on the resulting paper. I suppose I am a proper scientist now, rather than just a scientist larva.

The Atlantic meridional overturning circulation (AMOC for short) is an integral part of the global ocean conveyor belt. In the North Atlantic, a massive amount of water near the surface, cooling down on its way to the poles, becomes dense enough to sink. From there it goes on a thousand-year journey around the world – inching its way along the bottom of the ocean, looping around Antarctica – before finally warming up enough to rise back to the surface. A whole multitude of currents depend on the AMOC, most famously the Gulf Stream, which keeps Europe pleasantly warm.

Some have hypothesized that climate change might shut down the AMOC: the extra heat and freshwater (from melting ice) coming into the North Atlantic could conceivably lower the density of surface water enough to stop it sinking. This happened as the world was coming out of the last ice age, in an event known as the Younger Dryas: a huge ice sheet over North America suddenly gave way, drained into the North Atlantic, and shut down the AMOC. Europe, cut off from the Gulf Stream and at the mercy of the ice-albedo feedback, experienced another thousand years of glacial conditions.

A shutdown today would not lead to another ice age, but it could cause some serious regional cooling over Europe, among other impacts that we don’t fully understand. Today, though, there’s a lot less ice to start with. Could the AMOC still shut down? If not, how much will it weaken due to climate change? So far, scientists have answered these two questions with “probably not” and “something like 25%” respectively. In this study, we analysed 30 climate models (25 complex CMIP5 models, and 5 smaller, less complex EMICs) and came up with basically the same answer. It’s important to note that none of the models include dynamic ice sheets (computational glacial dynamics is a headache and a half), which might affect our results.

Models ran the four standard RCP experiments from 2006-2100. Not every model completed every RCP, and some extended their simulations to 2300 or 3000. In total, there were over 30 000 model years of data. We measured the “strength” of the AMOC using the standard unit Sv (Sverdrups), where each Sv is 1 million cubic metres of water per second.

Only two models simulated an AMOC collapse, and only at the tail end of the most extreme scenario (RCP8.5, which quite frankly gives me a stomachache). Bern3D, an EMIC from Switzerland, showed a MOC strength of essentially zero by the year 3000; CNRM-CM5, a GCM from France, stabilized near zero by 2300. In general, the models showed only a moderate weakening of the AMOC by 2100, with best estimates ranging from a 22% drop for RCP2.6 to a 40% drop for RCP8.5 (with respect to preindustrial conditions).

Are these somewhat-reassuring results trustworthy? Or is the Atlantic circulation in today’s climate models intrinsically too stable? Our model intercomparison also addressed that question, using a neat little scalar metric known as Fov: the net amount of freshwater travelling from the AMOC to the South Atlantic.

The current thinking in physical oceanography is that the AMOC is more or less binary – it’s either “on” or “off”. When AMOC strength is below a certain level (let’s call it A), its only stable state is “off”, and the strength will converge to zero as the currents shut down. When AMOC strength is above some other level (let’s call it B), its only stable state is “on”, and if you were to artificially shut it off, it would bounce right back up to its original level. However, when AMOC strength is between A and B, both conditions can be stable, so whether it’s on or off depends on where it started. This phenomenon is known as hysteresis, and is found in many systems in nature.

This figure was not part of the paper. I made it just now in MS Paint.

Here’s the key part: when AMOC strength is less than A or greater than B, Fov is positive and the system is monostable. When AMOC strength is between A and B, Fov is negative and the system is bistable. The physical justification for Fov is its association with the salt advection feedback, the sign of which is opposite Fov: positive Fov means the salt advection feedback is negative (i.e. stabilizing the current state, so monostable); a negative Fov means the salt advection feedback is positive (i.e. reinforcing changes in either direction, so bistable).

Most observational estimates (largely ocean reanalyses) have Fov as slightly negative. If models’ AMOCs really were too stable, their Fov‘s should be positive. In our intercomparison, we found both positives and negatives – the models were kind of all over the place with respect to Fov. So maybe some models are overly stable, but certainly not all of them, or even the majority.

As part of this project, I got to write a new section of code for the UVic model, which calculated Fov each timestep and included the annual mean in the model output. Software development on a large, established project with many contributors can be tricky, and the process involved a great deal of head-scratching, but it was a lot of fun. Programming is so satisfying.

Beyond that, my main contribution to the project was creating the figures and calculating the multi-model statistics, which got a bit unwieldy as the model count approached 30, but we made it work. I am now extremely well-versed in IDL graphics keywords, which I’m sure will come in handy again. Unfortunately I don’t think I can reproduce any figures here, as the paper’s not open-access.

I was pretty paranoid while coding and doing calculations, though – I kept worrying that I would make a mistake, never catch it, and have it dredged out by contrarians a decade later (“Kate-gate”, they would call it). As a climate scientist, I suppose that comes with the job these days. But I can live with it, because this stuff is just so darned interesting.

## The Hockey Stick and the Climate Wars

Throughout all the years of public disputes about climate change, arguably no scientist has taken as much flak as Dr. Michael Mann. This mild-mannered paleoclimatologist is frequently accused of fraud, incompetence, scientific malpractice, Communism, and orchestrating a New World Order. These charges have been proven baseless time and time again, but the accusations continue. Dr. Mann’s research on climate change is inconvenient for those who wish to deny that current global temperatures are unusual, so he has become the bulls-eye target in a fierce game of “shoot the messenger”. In “The Hockey Stick and the Climate Wars: Dispatches from the Front Lines”, a memoir of his experiences, Michael Mann finally speaks out.

The story begins quite harmlessly: an account of how he became a scientist, from childhood curiosity to graduate work in theoretical physics to choosing climate science on a whim out of the university course calendar. For those who have followed Dr. Mann’s research over the years, there is some great backstory – how he met his coauthors Ray Bradley and Malcolm Hughes, the formation of the IPCC TAR chapter about paleoclimate, and how the RealClimate blog operates. This book also filled in some more technical gaps in my understanding with a reasonably accessible explanation of principal component ananlysis, a summary of millennial paleoclimate research before 1998, and an explanation of exactly how Mann, Bradley and Hughes’ 2008 paper built on their previous work.

Dr. Mann’s 1998 paper – the “hockey stick” – was a breakthrough because it was the first millennial reconstruction of temperature that had global coverage and an annual resolution. He considered the recent dramatic rise in temperatures to be the least interesting part of their work, because it was already known from instrumental data, but that part of the paper got the most public attention.

It seems odd for a scientist to downplay the importance of his own work, but that’s what Dr. Mann does: he stresses that, without the hockey stick, the case for climate change wouldn’t be any weaker. Unfortunately, his work was overemphasized on all sides. It was never his idea to display the hockey stick graph so prominently in the IPCC TAR, or for activists to publicize his results the way they did. Soon the hockey stick became the holy grail of graphs for contrarians to destroy. As Ben Santer says, “There are people who believe that if they can bring down Mike Mann, they can bring down the IPCC,” and the entire field of climate science as a result.

Michael Mann is an eloquent writer, and does a fabulous job of building up tension. Most readers will know that he was the target of countless attacks from climate change deniers, but he withholds these experiences until halfway through the book, choosing instead to present more context to the story. The narrative keeps you on your toes, though, with frequent allusions to future events.

Then, when the full story comes out, it hits hard. Death threats, and a letter full of suspicious white powder. Lobby groups organizing student rallies against Mann on his own campus, and publishing daily attack ads in the campus newspaper. Discovering that his photo was posted as a “target” on a neo-Nazi website that insisted climate change was a Jewish conspiracy. A state politician from the education committee threatening to cut off funding to the entire university until they fired Mann.

Throughout these attacks, Dr. Mann consistently found trails to the energy industry-funded Scaife Foundation. However, I think he needs to be a bit more careful when he talks about the links between oil companies and climate change denial – the relationship is well-known, but it’s easy to come off sounding like a conspiracy theorist. Naomi Oreskes does a better job of communicating this area, in my opinion.

Despite his experiences, Michael Mann seems optimistic, and manages to end the book on a hopeful note about improvements in climate science communication. He is remarkably well-adjusted to the attacks against him, and seems willing to sacrifice his reputation for the greater good. “I can continue to live with the cynical assaults against my integrity and character by the corporate-funded denial machine,” he writes. “What I could not live with is knowing that I stood by silently as my fellow human beings, confused and misled by industry-funded propaganda, were unwittingly led down a tragic path that would mortgage future generations.”

“The Hockey Stick and the Climate Wars” leaves me with a tremendous empathy for Dr. Mann and all that he has gone through, as well as a far better understanding of the shouting match that dominates certain areas of the Internet and the media. It is among the best-written books on climate science I have read, and I would highly recommend it to all scientists and science enthusiasts.

“The Hockey Stick and the Climate Wars” will be released on March 6th, and the Kindle version is already available.

## How much is most?

A growing body of research is showing that humans are likely causing more than 100% of global warming: without our influences on the climate, the planet would actually be cooling slightly.

In 2007, the Intergovernmental Panel on Climate Change published its fourth assessment report, internationally regarded as the most credible summary of climate science to date. It concluded that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”.

A clear question remains: How much is “most”? 51%? 75%? 99%? At the time that the IPCC report was written, the answer was unclear. However, a new frontier of climate research has emerged since, and scientists are working hard to quantify the answer to this question.

I recently attended the 2011 American Geophysical Union Fall Meeting, a conference of over 20 000 scientists, many of whom study the climate system. This new area of research was a hot topic of discussion at AGU, and a phrase that came up many times was “more than 100%”.

That’s right, humans are probably causing more than 100% of observed global warming. That means that our influences are being offset by natural cooling factors. If we had never started burning fossil fuels, the world would be cooling slightly.

In the long term, oscillations of the Earth’s orbit show that, without human activity, we would be very slowly descending into a new ice age. There are other short-term cooling influences, though. Large volcanic eruptions, such as Mount Pinatubo in 1991, have thrown dust into the upper atmosphere where it blocks a small amount of sunlight. The sun, particularly in the last few years, has been less intense than usual, due to the 11-year sunspot cycle. We have also experienced several strong La Niña events in the Pacific Ocean, which move heat out of the atmosphere and into the ocean.

However, all of these cooling influences pale in comparison to the strength of the human-caused warming influences. The climate change communication project Skeptical Science recently summarized six scientific studies in this graphic:

Most of the studies estimated that humans caused over 100% of the warming since 1950, and all six put the number over 98%. Additionally, most of the studies find natural influences to be in the direction of cooling, and all six show that number to be close to zero.

If you are interested in the methodologies and uncertainty ranges of these six studies, Skeptical Science goes into more detail, and also provides links to the original journal articles.

To summarize, the perception that humans are accelerating a natural process of warming is false. We have created this problem entirely on our own. Luckily, that means we have the power to stop the problem in its tracks. We are in control, and we choose what happens in the future.

## Who are the Skeptics?

Part 3 in a series of 5 for NextGen Journal
Adapted from part of an earlier post

As we discussed last time, there is a remarkable level of scientific consensus on the reality and severity of human-caused global warming. However, most members of the public are unaware of this consensus – a topic which we will focus on in the next installment. Anyone with an Internet connection or a newspaper subscription will be able to tell you that many scientists think global warming is natural or nonexistent. As we know, these scientists are in the vast minority, but they have enjoyed widespread media coverage. Let’s look at three of the most prominent skeptics, and examine what they’re saying.

S. Fred Singer is an atmospheric physicist and retired environmental science professor. He has rarely published in scientific journals since the 1960s, but he is very visible in the media. In recent years, he has claimed that the Earth has been cooling since 1998 (in 2006), that the Earth is warming, but it is natural and unstoppable (in 2007), and that the warming is artificial and due to the urban heat island effect (in 2009).

Richard Lindzen, also an atmospheric physicist, is far more active in the scientific community than Singer. However, most of his publications, including the prestigious IPCC report to which he contributed, conclude that climate change is real and caused by humans. He has published two papers stating that climate change is not serious: a 2001 paper hypothesizing that clouds would provide a negative feedback to cancel out global warming, and a 2009 paper claiming that climate sensitivity (the amount of warming caused by a doubling of carbon dioxide) was very low. Both of these ideas were rebutted by the academic community, and Lindzen’s methodology criticized. Lindzen has even publicly retracted his 2001 cloud claim. Therefore, in his academic life, Lindzen appears to be a mainstream climate scientist – contributing to assessment reports, abandoning theories that are disproved, and publishing work that affirms the theory of anthropogenic climate change. However, when Lindzen talks to the media, his statements change. He has implied that the world is not warming by calling attention to the lack of warming in the Antarctic (in 2004) and the thickening of some parts of the Greenland ice sheet (in 2006), without explaining that both of these apparent contradictions are well understood by scientists and in no way disprove warming. He has also claimed that the observed warming is minimal and natural (in 2006).

Finally, Patrick Michaels is an ecological climatologist who occasionally publishes peer-reviewed studies, but none that support his more outlandish claims. In 2009 alone, Michaels said that the observed warming is below what computer models predicted, that natural variations in oceanic cycles such as El Niño explain most of the warming, and that human activity explains most of the warming but it’s nothing to worry about because technology will save us (cached copy, as the original was taken down).

While examining these arguments from skeptical scientists, something quickly becomes apparent: many of the arguments are contradictory. For example, how can the world be cooling if it is also warming naturally? Not only do the skeptics as a group seem unable to agree on a consistent explanation, some of the individuals either change their mind every year or believe two contradictory theories at the same time. Additionally, none of these arguments are supported by the peer-reviewed literature. They are all elementary misconceptions which were proven erroneous long ago. Multiple articles on this site could be devoted to rebutting such claims, but easy-to-read rebuttals for virtually every objection to human-caused climate change are already available on Skeptical Science. Here is a list of rebuttals relevant to the claims of Singer, Lindzen and Michaels:

With a little bit of research, the claims of these skeptics quickly fall apart. It does not seem possible that they are attempting to further our knowledge of science, as their arguments are so weak and inconsistent, and rarely published in scientific venues. However, their pattern of arguments does work as a media strategy, as most people will trust what a scientist says in the newspaper, and not research his reputation or remember his name. Over time, the public will start to remember dozens of so-called problems with the anthropogenic climate change theory.

## Is There Consensus?

Part 2 of a series of 5 for NextGen Journal

We hear the phrase “climate change consensus” tossed around all the time. But what does that even mean? And does it actually exist?

In Part 1 we discussed the concept of a scientific consensus: overwhelming agreement (but rarely unanimity) among experts. Of course, such a consensus could be wrong, but it wouldn’t be very sensible for the public to ignore it or bet against it. If 19 out of 20 doctors said you needed surgery to save your life, would you sit in the hospital bed and argue about their motives?

When it comes to climate change, the consensus view can be summarized as follows:

1. Human emissions of greenhouse gases, mainly from the burning of fossil fuels, are a significant force on the global climate.
2. The expected warming from this force is beginning to show up.

Often, people will write these two points in opposite order: the Earth is warming, and it’s due to our actions. However, that’s not the order that scientists discovered them. The academic community realized the Earth was going to warm decades before that warming became clear. Flipping around these observations might imply “that the entirety of climate science is based upon a single correlation study”.

So, what do the scientists say? In fact, publishing climatologists – the most specialized and knowledgeable people there with regards to climate change – are almost unanimous in their position. 96.2% say the Earth is warming, and 97.4% say humans are causing climate change. It’s hard to know why the second figure is higher than the first – perhaps one scientist in the study thought the effects of our actions hadn’t shown up yet (i.e., point 1 but not point 2).

A year later, others built on this study. They had a larger sample of climate scientists, 97-98% of whom agreed with the consensus position. Additionally, those who agreed had higher academic credibility than those who disagreed: they had published more papers (“expertise”) and been cited more times (“prominence”).

However, it doesn’t really matter what a scientist says, as much as how they back it up. Having a Ph.D. doesn’t mean you get to stop supporting your claims. In the academic community, this is done in the peer reviewed literature.

In 2004, a random sample of almost 1000 scientific studies on climate change were examined. 75% of the studies explicitly supported the consensus position, while the remaining 25% didn’t mention it – for example, some papers wrote about climate change millions of years ago, so today’s climate wasn’t relevant. Incredibly, not a single one disagreed with the consensus.

This still doesn’t imply unanimity – remember, it was a random sample, not the entire literature. A very few dissenting studies do get published each year, but they are such a tiny fraction of the total papers that it’s not surprising that none showed up in a sample of one thousand. Additionally, these papers generally fail to stand up to further scrutiny – their methods are often heavily critiqued by the academic community. See, for example, Lindzen and Choi, 2009 and its response.

It’s clear that individual polls have limitations. They are restricted to a sample of scientists or papers, rather than the entire community. They don’t take into account which claims stood the test of time, and which were refuted. Luckily, the climate science community has another way to summarize the balance of evidence on global warming: the Intergovernmental Panel on Climate Change (IPCC). Since 1988, four assessment reports have been written by thousands of volunteer scientists worldwide. They examine the entire body of academic literature on climate change and create a summary, which is then painstakingly reviewed and scrutinized by others.

The latest report, published in 2007, is already quite out of date – due to the long review process, most of the data is from 2002 and earlier. However, it is still used by governments worldwide, so let’s look at some of its key findings:

• “Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.”
• “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations.”
• “Anthropogenic warming over the last three decades has likely had a discernible influence at the global scale on observed changes in many physical and biological systems.”
• “Altered frequencies and intensities of extreme weather, together with sea level rise, are expected to have mostly adverse effects on natural and human systems.”
• “Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change.”

The final place to look for scientific consensus is statements from scientific organizations, such as the National Academy of Sciences. Not a single scientific organization worldwide disputes the consensus view, and many have published statements explicitly supporting it. A full list is available here, but here are some samples:

Climate change and sustainable energy supply are crucial challenges for the future of humanity. It is essential that world leaders agree on the emission reductions needed to combat negative consequences of anthropogenic climate change[.]

It is certain that increased greenhouse gas emissions from the burning of fossil fuels and from land use change lead to a warming of climate, and it is very likely that these green house gases are the dominant cause of the global warming that has been taking place over the last 50 years.
-Royal Society (UK)

The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society.
-American Association for the Advancement of Science

[C]omprehensive scientific assessments of our current and potential future climates clearly indicate that climate change is real, largely attributable to emissions from human activities, and potentially a very serious problem.
-American Chemical Society

Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth’s climate…The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.
-American Physical Society

The Earth’s climate is now clearly out of balance and is warming. Many components of the climate system…are now changing at rates and in patterns that are not natural and are best explained by the increased atmospheric abundances of greenhouse gases and aerosols generated by human activity during the 20th century.
-American Geophysical Union

It’s clear that a scientific consensus on climate change does exist. Since unanimity is virtually impossible in science, agreement over climate change can’t get much stronger than it is already.

Could all of these scientists, papers, reports, and organizations be wrong? Of course – nobody is infallible. Could that 3% of dissenting scientists triumph like Galileo? It’s possible.

But how much are you willing to risk on that chance?

## Quality, Transparency, and Rigour

The Intergovernmental Panel on Climate Change (IPCC) reports are likely the most cited documents on the subject of global warming. The organization, established by the United Nations, doesn’t do any original research – it simply summarizes the massive amount of scientific literature on the topic. Their reports, written and reviewed by volunteer scientists, and published approximately every six years, are a “one-stop shop” for credible information about climate change. When you have a question about climate science, it’s far easier to find the relevant section of the IPCC than it is to wade through thousands of results on Google Scholar.

The main problem with the IPCC, in my opinion, is that their reports are out of date as soon as they’re published, and then everyone has to wait another six years or so for the next version, which is subsequently out of date, and so on. Additionally, because there are so many authors, reviewers, and stakeholders involved in the IPCC, the reports come to reflect the lowest-common-denominator scientific understanding, rather than the median opinion of experts. In particular, government officials oversee the writing and reviewing of the Summary for Policymakers, to make sure that it’s relevant and clear. However, some governments are beginning to abuse their power in this process. The late Stephen Schneider, in his 2009 book Science as a Contact Sport, recounts his experiences with government representatives who absolutely refuse to allow certain conclusions to be published in the IPCC, regardless of their scientific backing.

The result is that the IPCC reports frequently underestimate the severity of climate change. For example, in the most recent report, the worst-case estimate of sea level rise by the end of this century was 0.59 m. Since then, scientists have revised this estimate to 1.9 m, but it won’t show up in the report until the next edition comes out around 2014.

Another example concerns Arctic sea ice: the worst-case scenario from the IPCC was an ice-free Arctic in the summer beginning around 2100. These estimates have come down so rapidly that there’s an outside chance the summer sea ice could be gone before the next IPCC report has a chance to correct it (presentation by Dr. David Barber, media coverage available here). It will more likely disappear around 2035, but that’s still a drastic change from what the IPCC said.

Despite this conservative stance, there are still some who think the IPCC is alarmist (this is usually paired with something about a New World Order and/or socialists using a carbon tax to take over the world). Naturally, the IPCC has become a favourite target of climate change deniers, who wish to obscure the reality of human-caused global warming. Last year, they claimed to have found all kinds of errors in the latest report, somehow proving that global warming wasn’t happening. In fact, most of these so-called “errors” were nothing of the sort, and the worst of the two real mistakes in the report involved a typo regarding which year certain glaicers were expected to disappear. Not bad, for a three-thousand-page document, but it created quite the media firestorm. Apparently scientists are expected to have 100% accuracy at all times, or else they are frauds.

Just a few weeks ago, the IPCC made some changes to their policies in response to these events. Their press release about the new policies featured the phrase ”Boost Quality, Transparency and Rigour” in the title.

No, no, no. That’s not what the IPCC needs. These are very admirable goals, but they’re doing just fine as it is. Actions to ”further minimize any possibility of errors in future reports” should not be their top priority. Further extending the review process will only further delay the publication of each report (making them even more out of date) and further enhance their lowest-common-denominator position. When you have an error rate on the order of 0.67 errors/1000 pages, should you spend your energy getting that all the way down to zero (a virtually impossible task) or on the real issues that need to be addressed?

I think the IPCC should adopt a continually-updating online version of their report. This would solve their chronic problem of being out of date, as well as help the organization adapt to the increasing role of the Internet in our world. Any future errors the deniers liked to yell about would be fixed immediately. Governments would be forming policies based on the best available evidence from today, not a decade ago. Everything would still be in one place, and version control would allow transparency to remain high.

The IPCC should also make it more clear when their estimates are too conservative. When a single sentence that didn’t even make it into the summary is shown to overestimate the problem, the climate science community ties itself up in knots trying to correct its tattered image. But prominent conclusions that underestimate the problem go unacknowledged for decades. If it were the other way around, can you imagine the field day deniers would have?

Luckily, the changes made to IPCC policy are not all aimed at appeasing the bullies. A long-overdue communications plan is in development: a rapid response team and Senior Communications Manager will develop formal strategies for public education and outreach. Hopefully, this will counteract the false claims and defamation the IPCC has been subject to since its creation.

Another new plan is to create an Executive Committee, composed of the Chair, Vice Chairs, Working Group Co-Chairs, and advisory members. This will “strengthen coordination and management of the IPCC” and allow for actions to be taken between reports, such as communication and responding to possible errors. A more structured administration will probably be helpful, given that the only people in the organization currently getting paid for their work are the office staff (even the Chair doesn’t make a cent). Coordinating overworked scientists who volunteer for a scientific undertaking that demands 100% accuracy can’t be an easy task.

Will the IPCC continue to be the best available source of credible information on climate change? Will its structure of endless review remain feasible in a world dominated by instant news? Should we continue to grant our governments control over the contents of scientific reports concerning an issue that they desperately want to avoid? Should we continue to play to the wants and needs of bullies? Or should we let scientists speak for themselves?

## Beautiful Things

This is what the last few days have taught me: even if the code for climate models can seem dense and confusing, the output is absolutely amazing.

Late yesterday I discovered a page of plots and animations from the Canadian Centre for Climate Modelling and Analysis. The most recent coupled global model represented on that page is CGCM3, so I looked at those animations. I noticed something very interesting: the North Atlantic, independent of the emissions scenario, was projected to cool slightly, while the world around it warmed up. Here is an example, from the A1B scenario. Don’t worry if the animation is already at the end, it will loop:

It turns out that this slight cooling is due to the North Atlantic circulation slowing down, as is very likely to happen from large additions of freshwater that change the salinity and density of the ocean (IPCC AR4 WG1, FAQ 10.2). This freshwater could come from either increased precipitation due to climate change, or meltwater from the Arctic ending up in the North Atlantic. Of course, we hear about this all the time – the unlikely prospect of the Gulf Stream completely shutting down and Europe going into an ice age, as displayed in The Day After Tomorrow - but, until now, I hadn’t realized that even a slight slowing of the circulation could cool the North Atlantic, while Europe remained unaffected.

Then, in chapter 8 of the IPCC, I read something that surprised me: climate models generate their own El Ninos and La Ninas. Scientists don’t understand quite what triggers the circulation patterns leading to these phenomena, so how can they be in the models? It turns out that the modellers don’t have to parameterize the ENSO cycles at all: they have done such a good job of reproducing global circulation from first principles that ENSO arises by itself, even though we don’t know why. How cool is that? (Thanks to Jim Prall and Things Break for their help with this puzzle.)

Jim Prall also pointed me to an HD animation of output from the UK-Japan Climate Collaboration. I can’t seem to embed the QuickTime movie (WordPress strips out some of the necessary HTML tags) so you will have to click on the link to watch it. It’s pretty long – almost 17 minutes – as it represents an entire year of the world’s climate system, in one-hour time steps. It shows 1978-79, starting from observational data, but from there it simulates its own circulation.

I am struck by the beauty of this output – the swirling cyclonic precipitation, the steady prevailing westerlies and trade winds, the subtropical high pressure belt clear from the relative absence of cloud cover in these regions. You can see storms sprinkling across the Amazon Basin, monsoons pounding South Asia, and sea ice at both poles advancing and retreating with the seasons. Scientists didn’t explicitly tell their models to do any of this. It all appeared from first principles.

Take 17 minutes out of your day to watch it – it’s an amazing stress reliever, sort of like meditation. Or maybe that’s just me…

One more quick observation: most of you are probably familiar with the naming conventions of IPCC reports. The First Assessment Report was FAR, the second was SAR, and so on, until the acronyms started to repeat themselves, so the Fourth Assessment Report was AR4. They’ll have to follow this alternate convention until the Eighth Annual Report, which will be EAR. Maybe they’ll stick with AR8, but that would be substantially less entertaining.

## What Can One Person Do?

Next week, I will be giving a speech on climate change to the green committee of a local United Church. They are particularly interested in science and solutions, so I wrote the following script, drawing heavily from my previous presentations. I would really appreciate feedback and suggestions for this presentation.

Citations will be on the slides (which I haven’t made yet), so they’re not in the text of this script. Let me know if there’s a particular reference you’re wondering about, but they’re probably common knowledge within this community by now.

Enjoy!

Climate change is depressing. I know that really well, because I’ve been studying it for over two years. I’m quite practiced at keeping the scary stuff contained in the analytical part of my brain, and not thinking of the implications – because the implications make you feel powerless. I’m sure that all of us here wish we could stop global warming on our own. So we work hard to reduce our carbon footprints, and then we feel guilty every time we take the car out or buy something that was made in China or turn up the heat a degree.

The truth is, though, the infrastructure of our society doesn’t support a low-carbon lifestyle. Look at the quality of public transit in Winnipeg, or the price of local food. We can work all we want at changing our practices, but it’s an uphill battle. If we change the infrastructure, though – if we put a price on carbon so that sustainable practices are cheaper and easier than using fossil fuels – people everywhere will subsequently change their practices.

Currently, governments – particularly in North America – aren’t too interested in sustainable infrastructure, because they don’t think people care. Politicians only say what they think people want to hear. So, should we go dress up as polar bears and protest in front of Parliament to show them we care? That might work, but they will probably just see us as crazy environmentalists, a fringe group. We need a critical mass of people that care about climate change, understand the problem, and want to fix it. An effective solution requires top-down organization, but that won’t happen until there’s a bottom-up, grassroots movement of people who care.

I believe that the most effective action one person can take in the fight against global warming is to talk to others and educate others. I believe most people are good, and sane, and reasonable. They do the best they can, given their level of awareness. If we increase that awareness, we’ll gain political will for a solution. And so, in an effort to practice what I preach, I’m going to talk to you about the issue.

The science that led us to the modern concern about climate change began all the way back in 1824, when a man named Joseph Fourier discovered the greenhouse effect. Gases such as carbon dioxide make up less than one percent of the Earth’s atmosphere, but they trap enough heat to keep the Earth over 30 degrees Celsius warmer than it would be otherwise.

Without greenhouse gases, there could be no life on Earth, so they’re a very good thing – until their concentration changes. If you double the amount of CO2 in the air, the planet will warm, on average, somewhere around 3 degrees. The first person to realize that humans could cause this kind of a change, through the burning of fossil fuels releasing CO2, was Svante Arrhenius, in 1897. So this is not a new theory by any means.

For a long time, scientists assumed that any CO2 we emitted would just get absorbed by the oceans. In 1957, Roger Revelle showed that wasn’t true. The very next year, Charles Keeling decided to test this out, and started measuring the carbon dioxide content of the atmosphere. Now, Arrhenius had assumed that it would take thousands of years to double CO2 from the preindustrial value of 280 ppm (which we know from ice cores), but the way we’re going, we’ll get there in just a few decades. We’ve already reached 390 ppm. That might not seem like a lot, but 390 ppm of arsenic in your coffee would kill you. Small changes can have big effects.

Around the 1970s, scientists realized that people were exerting another influence on the climate. Many forms of air pollution, known as aerosols, have a cooling effect on the planet. In the 70s, the warming from greenhouse gases and the cooling from aerosols were cancelling each other out, and scientists were split as to which way it would go. There was one paper, by Stephen Schneider, which even said it could be possible to cause an ice age, if we put out enough aerosols and greenhouse gases stayed constant. However, as climate models improved, and governments started to regulate air pollution, a scientific consensus emerged that greenhouse gases would win out. Global warming was coming – it was just a question of when.

In 1988, James Hansen, who is arguably the top climate scientist in the world today, claimed it had arrived. In a famous testimony to the U.S. Congress, he said that “the greenhouse effect has been detected, and it is changing our climate now.” Many scientists weren’t so sure, and thought it was too early to make such a bold statement, but Hansen turned out to be right. Since about 1975, the world has been warming, more quickly than it has for at least the last 55 million years.

Over the past decade, scientists have even been able to rule out the possibility that the warming is caused by something else, like a natural cycle. Different causes of climate change have slightly different effects – like the pattern of warming in different layers of the atmosphere, the amount of warming in summer compared to winter, or at night compared to in the day, and so on. Ben Santer pioneered attribution studies: examining these effects in order to pinpoint a specific cause. And so far, nobody has been able to explain how the recent warming could not be caused by us.

Today, there is a remarkable amount of scientific agreement surrounding this issue. Between 97 and 98% of climate scientists, virtually 100% of peer-reviewed studies, and every scientific organization in the world agree that humans are causing the Earth to warm. The evidence for climate change is not a house of cards, where you take one piece out and the whole theory falls apart. It’s more like a mountain. Scrape a handful of pebbles off the top, but the mountain is still there.

However, if you take a step outside of the academic community, this convergence of evidence is more or less invisible. The majority of newspaper articles, from respected outlets like the New York Times or the Wall Street Journal, spend at least as much time arguing against this consensus as they do arguing for it. They present ideas such as “maybe it’s a natural cycle” or “CO2 has no effect on climate” that scientists disproved years ago. The media is stuck in the past. Some of them are only stuck in the 1980s, but others are stuck all the way back in 1800. Why is it like this?

Part of it comes from good, but misguided, intentions. When it comes to climate change, most journalists follow the rule of balance: presenting “two equal sides”, staying neutral, letting the reader form their own opinion. This works well when the so-called controversy is one of political or social nature, like tax levels or capital punishment. In these cases, there is no right answer, and people are usually split into two camps. But when the question at hand is one of science, there is a right answer – even if we haven’t found it yet – so some explanations are better than others, and some can be totally wrong. Would you let somebody form their own opinion on Newton’s Laws of Motion or the reality of photosynthesis? Sometimes scientists are split into two equal groups, but sometimes they’re split into three or four or even a dozen. How do you represent that as two equal sides? Sometimes, like we see with climate change, pretty much all the scientists are in agreement, and the two or three percent which aren’t don’t really publish, because they can’t back up their statements and nobody really takes them seriously. So framing these two groups as having equal weight in the scientific community is completely incorrect. It exaggerates the extreme minority, and suppresses everyone else. Being objective is not always the same as being neutral, and it’s particularly important to remember that when our future is at stake.

Another reason to frame climate science as controversial is that it makes for a much better story. Who really wants to read about scientists agreeing on everything? Journalists try to write stories that are exciting. Unfortunately, that goal can begin to overshadow accuracy.

Also, there are fewer journalists than there used to be, and there are almost no science journalists in the mainstream media – general reporters cover science issues instead. Also, a few decades ago, journalists used to get a week or two to write a story. Now they often have less than a day, because speed and availability of news has become more important than quality.

However, perhaps the most important – and disturbing – explanation for this inaccurate framing is that the media has been very compliant in spreading the message of climate change deniers. They call themselves skeptics, but I don’t think that’s accurate. A true skeptic will only accept a claim given sufficient evidence. That’s a good thing, and all scientists should be skeptics. But it’s easy to see that these people will never accept human-caused climate change, no matter what the evidence. At the same time, they blindly accept any shred of information that seems to support their cause, without applying any skepticism at all. That’s denial, so let’s not compliment them by calling them skeptics.

Climate change deniers will use whatever they can get – whether or not it’s legitimate, whether or not it’s honest – as proof that climate change is natural, or nonexistent, or a global conspiracy. They’ll tell you that volcanoes emit more CO2 than humans, but volcanoes actually emit about 1% of what we do. They’ll say that global warming has stopped because 2008 was cooler than 2007. If climatologists organize a public lecture in effort to communicate accurate scientific information, they’ll say that scientists are dogmatic and subscribe to censorship and will not allow any other opinions to be considered.

Some of these questionable sources are organizations, like a dozen or so lobby groups that have been paid a lot of money by oil companies to say that global warming is fake. Some of them are individuals, like US Senator James Inhofe, who was the environment chair under George W. Bush, and says that “global warming is the greatest hoax ever imposed upon the American people.” Some of them have financial motivations, and some of them have ideological motivations, but their motivations don’t really matter – all that matters is that they are saying things that are inaccurate, and misleading, and just plain wrong.

There has been a recent, and very disturbing, new tactic of deniers. Instead of attacking the science, they’ve begun to attack the integrity of individual scientists. In November 2009, they stole thirteen years of emails from a top climate research group in the UK, and spread stories all over the media that said scientists were caught fudging their data and censoring critics. Since then, they’ve been cleared of these charges by eight independent investigations, but you wouldn’t know it by reading the newspaper. For months, nearly every media outlet in the developed world spread what was, essentially, libel, and the only one that has formally apologized for its inaccurate coverage is the BBC.

In the meantime, there has been tremendous personal impact on the scientists involved. Many of them have received death threats, and Phil Jones, the director of the research group, was nearly driven to suicide. Another scientist, who wishes to remain anonymous, had a dead animal dumped on his doorstep and now travels with bodyguards. The Republican Party, which prides itself on fiscal responsibility, is pushing for more and more investigations, because they just can’t accept that the scientists are innocent…and James Inhofe, the “global warming is a hoax” guy, attempted to criminally prosecute seventeen researchers, most of whom had done nothing but occasionally correspond with the scientists who had their emails stolen. It’s McCarthyism all over again.

So this is where we are. Where are we going?

The Intergovernmental Panel on Climate Change, or IPCC, which collects and summarizes all the scientific literature about climate change, said in 2007 that under a business-as-usual scenario, where we keep going the way we’re going, the world will warm somewhere around 4 degrees Celsius by 2100. Unfortunately, this report was out of date almost as soon as it was published, and has widely been criticized for being too conservative. The British Meteorological Office published an updated figure in 2009 that estimated we will reach 4 degrees by the 2070s.

I will still be alive then (I hope!). I will likely have kids and even grandkids by then. I’ve spent a lot of time researching climate change, and the prospect of a 4 degree rise is terrifying to me. At 4 degrees, we will have lost control of the climate – even if we stop emitting greenhouse gases, positive feedbacks in the climate system will make sure the warming continues. We will have committed somewhere between 40 and 70 percent of the world’s species to extinction. Prehistoric records indicate that we can expect 40 to 80 metres of eventual sea level rise – it will take thousands of years to get there, but many coastal cities will be swamped within the first century. Countries – maybe even developed countries – will be at war over food and water. All this…within my lifetime.

And look at our current response. We seem to be spending more time attacking the scientists who discovered the problem than we are negotiating policy to fix it. We should have started reducing our greenhouse gas emissions twenty years ago, but if we start now, and work really hard, we do have a shot at stopping the warming at a point where we stay in control. Technically, we can do it. It’s going to take an unprecedented amount of political will and international communication

Everybody wants to know, “What can I do?” to fix the problem. Now, magazines everywhere are happy to tell you “10 easy ways to reduce your carbon footprint” – ride your bike, and compost, and buy organic spinach. That’s not really going to help. Say that enough people reduce their demand on fossil fuels: supply and demand dictates that the price will go down, and someone else will say, “Hey, gas is cheap!” and use more of it. Grassroots sentiment isn’t going to be enough. We need a price on carbon, whether it’s a carbon tax or cap-and-trade…but governments won’t do that until a critical mass of people demand it.

So what can you do? You can work on achieving that critical mass. Engage the apathetic. Educate people. Talk to them about climate change – it’s scary stuff, but suck it up. We’re all going to need to face it. Help them to understand and care about the problem. Don’t worry about the crazy people who shout about socialist conspiracies, they’re not worth your time. They’re very loud, but there’s not really very many of them. And in the end, we all get one vote.

## Climate Scientists Out in the Cold

Cross-posted from NextGen Journal

In the current economy, it’s not surprising that many countries are reducing funds for scientific research. It’s necessary to cut spending across the board these days. However, North American governments are singling out climate science as a victim – and not just reducing its funding, but, in many cases, eliminating it altogether.

Climate change research is largely supported by government money, as there aren’t many industries that recognize a vested interest in the science. Pharmaceutical companies often fund biomedical researchers, and mining companies fund geologists, but there’s no real analogue for climate scientists. Additionally, many global warming studies are particularly expensive. For example, transporting researchers and equipment to the North Pole via helicopter, and building climate models on supercomputers that stretch the limits of our data storage capacities, cost quite a bit more than injecting rats with chemicals in a lab.

In Canada, where I live, the federal government recognized these unique characteristics of climate science, and, in 2000, set up a special foundation to fund research in the field: the Canadian Foundation for Climate and Atmospheric Sciences (CFCAS). Over the past decade, it has spent \$118 million supporting most of Canada’s university-based climate research, and it was assumed that it would be continually renewed as the country established itself as a leader in the field.

However, since the Conservative Party formed a minority government almost five years ago, it has only extended the foundation’s lifespan by a year, and refuses to consider long-term funding commitments. The CFCAS only has a few months left before it will run out of money and close its doors. Many of Canada’s premier climate research projects and laboratories will have to shut down as a result, as they have always relied on CFCAS, and general federal funds such as the National Science and Engineering Research Council (NSERC) simply won’t be able to fill the gap. Some researchers are leaving the country to pursue more fertile academic ground, and as an aspiring climate scientist, I am wondering whether I will have to eventually do so as well.

If it seems cruel to abandon funding for researching the greatest threat to our future, rather than simply reducing its budget until the economy recovers, take a stroll south to what my sociology professor likes to refer to as “that wild society”. The U.S. House of Representatives is becoming dominated by politicians who hate the idea of government, and wish to tear most of it down in anger. Add to that mindset a staunch denial of climate science, and you can see where this is going.

The House of Representatives just passed a bill that not only prevents the Environmental Protection Agency from regulating greenhouse gases that cause climate change, but also repeals a great deal of clean air and water protection. Other cornerstones of the bill include repealing the new American health care system and cutting off funding of Planned Parenthood.

Since not a single Democrat Member of Congress voted for this bill, it is unlikely to pass the Senate, where Democrats hold a majority. However, Republicans have threatened to take away all federal funding, effectively shutting down the entire U.S. government, if the bill is not passed into law.

An amendment to this bill, which also passed the House of Representatives, completely cuts off federal funding to the Intergovernmental Panel on Climate Change (IPCC). The IPCC, a scientific organization of the United Nations, doesn’t do any original research, but writes extensive summary reports of the academic literature on climate change. It’s hard to overestimate how important these reports, published every few years, are to governments, scientists, and citizens alike. Instead of having to dig through thousands of scientific journals and articles, with no idea where to start, people can simply read these reports to find out what science knows about climate change. They are painstakingly reviewed, are offered in several levels of technicality, and include carefully organized references to the multitude of studies whose conclusions contributed to the text. For a field of research that is quickly expanding, these reports are absolutely vital, and it’s hard to imagine how they could carry on without support from the American government.

Blaine Luetkemeyer, the Republican Member of Congress that proposed the amendment, justified cutting off the IPCC by asserting the oft-debunked, but disturbingly popular, meme that climate science is some kind of worldwide conspiracy. If the IPCC really is “corrupt” and “nefarious”, as Luetkemeyer claims, then why can’t they afford to pay any of the scientists that write the reports – not even the IPCC president? Why do they allow anyone to help review the draft reports? Why do they permit their Summary for Policymakers to be watered down by policymakers? And, most importantly, why is climate change progressing faster than the IPCC expected?

We shouldn’t have to spend time addressing paranoid conspiracy theories like Luetkemeyer’s . Sadly, the government of the most powerful country on Earth is being taken over by people who buy into these conspiracy theories, and who want to punish climate scientists as much as possible for crimes they haven’t committed. Countries like Canada, even if they refrain from public accusations, are following suit in their actions.

“It’s quite clear by their actions [with CFCAS] and its lack of funding that [the Canadian government is] basically saying ‘We don’t want your science any more’,” Andrew Weaver, Canada’s top climatologist, told the Globe and Mail.

“[Cutting off the IPCC] is like putting our heads in the sand, denying the science, and then stopping the scientists from working – because they might come to a different conclusion from the Republican Party’s ideology,” Democrat Member of Congress Henry Waxman argued.

Is this really a wise move?