Posts Tagged ‘greenhouse effect’

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.

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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.


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.

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“It is remarkable and untenable that the second largest forcing
that drives global climate change remains unmeasured,” writes Dr. James Hansen, the head of NASA’s climate change research team, and arguably the world’s top climatologist.

The word “forcing” refers to a factor, such as changes in the Sun’s output or in atmospheric composition, that exerts a warming or cooling influence on the Earth’s climate. The climate doesn’t magically change for no reason – it is always driven by something. Scientists measure these forcings in Watts per square metre – imagine a Christmas tree lightbulb over every square metre of the Earth’s surface, and you have 1 W/m2 of positive forcing.

Currently, the largest forcing on the Earth’s climate is that of increasing greenhouse gases from burning fossil fuels. These exert a positive, or warming, forcing, hence the term “global warming”. However, a portion of this positive forcing is being cancelled out by the second-largest forcing, which is also anthropogenic. Many forms of air pollution, collectively known as aerosols, exert a negative (cooling) forcing on the Earth’s climate. They do this in two ways: the direct albedo effect (scattering solar radiation so it never reaches the planet), and the indirect albedo effect (providing surfaces for clouds to form and scatter radiation by themselves). A large positive forcing and a medium negative forcing sums out to a moderate increase in global temperatures.

Unfortunately, a catch-22 exists with aerosols. As many aerosols are directly harmful to human health, the world is beginning to regulate them through legislation such as the American Clean Air Act. As this pollution decreases, its detrimental health effects will lessen, but so will its ability to partially cancel out global warming.

The problem is that we don’t know how much warming the aerosols are cancelling – that is, we don’t know the magnitude of the forcing. So, if all air pollution ceased tomorrow, the world could experience a small jump in net forcing, or a large jump. Global warming would suddenly become much worse, but we don’t know just how much.

The forcing from greenhouse gases is known with a high degree of accuracy – it’s just under 3 W/m2. However, all we know about aerosol forcing is that it’s somewhere around -1 or -2 W/m2 – an estimate is the best we can do. The reason for this dichotomy lies in the ease of measurement. Greenhouse gases last a long time (on the order of centuries) in the atmosphere, and mix through the air, moving towards a uniform concentration. An air sample from a remote area of the world, such as Antarctica or parts of Hawaii, will be uncontaminated by cars and factories nearby, and will contain an accurate value of the global atmospheric carbon dioxide concentration (the same can be done for other greenhouse gases, such as methane) . From these measurements, molecular physics can tell us how large the forcing is. Direct records of carbon dioxide concentrations have been kept since the late 1950s:

However, aerosols only stay in the troposphere for a few days, as precipitation washes them out of the air. For this reason, they don’t have time to disperse evenly, and measurements are not so simple. The only way to gain accurate measurements of their concentrations is with a satellite. NASA recently launched the Glory satellite for just this purpose. Unfortunately, it failed to reach orbit (an inherent risk for satellites), and given the current political climate in the United States, it seems overly optimistic to hope for funding for a new one any time soon. Luckily, if this project was carried out by the private sector, without the need for money-draining government review panels, James Hansen estimates that it could be achieved with a budget of around $100 million.

An accurate value for aerosol forcing can only be achieved with accurate measurements of aerosol concentration. Knowing this forcing would be immensely helpful for climate researchers, as it impacts not only the amount of warming we can expect, but also how long it will take to play out, until the planet reaches thermal equilibrium. Aimed with better knowledge of these details will allow policymakers to better plan for the future, regarding both mitigation of and adaptation to climate change. Finally measuring the impact of aerosols, instead of just estimating, could give our understanding of the climate system the biggest bang for its buck.

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“Global warming…doesn’t that have something to do with the ozone?” Well, no. Environmental issues are not all the same. It’s common for people to confuse climate change and ozone depletion, but they are separate issues – although they are indirectly connected in some interesting ways.

Ozone, which is made of three oxygen atoms stuck together (instead of two, which is what normal oxygen gas is made of), is vital to life on Earth. It forms a layer in the stratosphere, the second layer up in the atmosphere, that is very good at absorbing ultraviolet (UV) radiation from the Sun. UV radiation severely damages organisms if enough of it reaches the surface. The 3% or less that gets through the ozone already gives us sunburns and skin cancer, so you can imagine what the situation would be like if the ozone layer wasn’t there at all.

In the middle of the 20th century, synthetic gases known as chlorofluorocarbons (CFCs) became popular for use in refrigerators and aerosol products, among other applications. They were non-toxic, and did not react easily with other substances, so they were used widely. However, their chemical stability allowed them to last long enough to drift into the stratosphere after they were emitted.

Once in the stratosphere, the CFCs were exposed to UV radiation, which was able to break them down. Free chlorine atoms (Cl) were liberated, a substance that is very reactive indeed. In fact, Cl acts as a catalyst in the decomposition of ozone, allowing two ozone molecules to become three oxygen molecules, losing their UV absorbing power in the process. Since catalysts are not used up in a reaction, the same Cl radical can continue to destroy ozone until it reacts with something else in the atmosphere and is removed.

Over the poles, the stratosphere is cold enough for polar stratospheric clouds (PSCs) to form. These PSCs provided optimum conditions for the most reactive chlorine gas of all to form: ClO (chlorine monoxide). Now there wasn’t just a catalytic cycle of free Cl radicals depleting the ozone, there was also a cycle of ClO. It turns out that Antarctica was more favourable for ozone depletion than the Arctic, both because its temperatures were lower and because its system of wind currents prevented the ozone-depleting substances from drifting out of the area.

Before long, there was a hole in the ozone layer over Antarctica (due to the PSCs), and concentrations were declining in other locations too (due to the basic Cl reactions). The issue became a frontier for scientific research, and scientists Crutzen, Rowland, and Molina won the 1995 Nobel Prize in Chemistry for their work with atmospheric ozone.

In 1987, politicians worldwide decided to ban CFCs under the Montreal Protocol. This movement was largely successful, and the use of CFCs has become nearly negligible, especially in developed nations. They have been replaced with gases that safely decompose before they reach the stratosphere, so they don’t interfere with ozone. The regulations are working: the ozone hole in Antarctica has stabilized, and global stratospheric ozone concentrations have been on the rise since 1993.

In contrast, climate change is a product of greenhouse gases such as carbon dioxide. Unlike CFCs, most of them are not synthetic, and they are released from the burning of fossil fuels (coal, oil, and natural gas), not specific products such as refrigerators. Rather than destroying a natural process, like CFCs do, they strengthen one to the point of harm: the greenhouse effect. This phenomenon, which traps heat in the atmosphere, is absolutely vital, as the Earth would be too cold to support life without it. Increasing the concentrations of greenhouse gases with fossil fuels becomes too much of a good thing, though, as the greenhouse effect traps more heat, warming the planet up.

Just a few degrees Celsius of warming can cause major problems, as agricultural zones, wind and ocean currents, and precipitation patterns shift. The sea level rises, submerging coastal cities. Many species go extinct, as the climate changes faster than they can adapt. Basically, the definition of “normal” in which our civilization has developed and thrived is changing, and we can’t count on that stability any more.

Unlike the Montreal Protocol, efforts to reduce greenhouse gas emissions have more or less failed. Fossil fuels permeate every part of our lives, and until we shift the economy to run on clean energy instead, convincing governments to commit to reductions will be difficult at best. It remains to be seen whether or not we can successfully address this problem, like we did with ozone depletion.

Although these two issues are separate, they have some interesting connections. For example, PSCs form in cold areas of the stratosphere. That’s why the ozone hole is over Antarctica, and not somewhere else. Unfortunately, global warming is, paradoxically, cooling the stratosphere, as a stronger greenhouse effect means that less heat reaches the stratosphere. Therefore, as climate change progresses, it will make it easier for the ozone depletion reactions to occur, even though there are fewer CFCs.

Additionally, CFCs are very strong greenhouse gases, but their use has drastically reduced so their radiative effects are of lesser concern to us. However, some of their replacements, HFCs, are greenhouse gases of similar strength. They don’t deplete the ozone, but, per molecule, they can be thousands of times stronger than carbon dioxide at trapping heat. Currently, their atmospheric concentrations are low enough that they contribute far less forcing than carbon dioxide, but it wouldn’t take a large increase in HFCs to put us in a bad situation, simply because they are so potent.

Finally, these two issues are similar in that ozone depletion provides a smaller-scale analogue for the kinds of political and economic changes we will have to make to address climate change:

  1. Unintended chemical side effects of our economy posed a serious threat to all species, including our own.
  2. Industry representatives and free-market fundamentalists fought tooth and nail against conclusive scientific findings, and the public became bewildered in a sea of misinformation.
  3. Governments worked together to find sensible alternatives and more or less solved the problem.

We’ve already seen the first two events happen with climate change. Will we see the third as well?

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Life on Earth does not enjoy change, and climate change is something it likes least of all. Every aspect of an organism’s life depends on climate, so if that variable changes, everything else changes too – the availability of food and water, the timing of migration or hibernation, even the ability of bodily systems to keep running.

Species can adapt to gradual changes in their environment through evolution, but climate change often moves too quickly for them to do so. It’s not the absolute temperature, then, but the rate of change that matters. Woolly mammoths and saber-toothed tigers thrived during the Ice Ages, but if the world were to shift back to that climate overnight, we would be in trouble.

Put simply, if climate change is large enough, quick enough, and on a global scale, it can be the perfect ingredient for a mass extinction. This is worrying, as we are currently at the crux of a potentially devastating period of global warming, one that we are causing. Will our actions cause a mass extinction a few centuries down the line? We can’t tell the future of evolution, but we can look at the past for reference points.

There have been five major extinction events in the Earth’s history, which biologists refer to as “The Big Five”. The Ordovician-Silurian, Late Devonian, Permian-Triassic, Late Triassic, Cretaceous-Tertiary…they’re a bit of a mouthful, but all five happened before humans were around, and all five are associated with climate change. Let’s look at a few examples.

The most recent extinction event, the Cretaceous-Tertiary (K-T) extinction, is also the most well-known and extensively studied: it’s the event that killed the dinosaurs. Scientists are quite sure that the trigger for this extinction was an asteroid that crashed into the planet, leaving a crater near the present-day Yucatan Peninsula of Mexico. Devastation at the site would have been massive, but it was the indirect, climatic effects of the impact that killed species across the globe. Most prominently, dust and aerosols kicked up by the asteroid became trapped in the atmosphere, blocking and reflecting sunlight. As well as causing a dramatic, short-term cooling, the lack of sunlight reaching the Earth inhibited photosynthesis, so many plant species became extinct. This effect was carried up the food chain, as first herbivorous, then carnivorous, species became extinct. Dinosaurs, the dominant life form during the Cretaceous Period, completely died out, while insects, early mammals, and bird-like reptiles survived, as their small size and scavenging habits made it easier to find food.

However, life on Earth has been through worse than this apocalyptic scenario. The
largest extinction in the Earth’s history, the Permian-Triassic extinction, occurred about 250 million years ago, right before the time of the dinosaurs. Up to 95% of all species on Earth were killed in this event, and life in the oceans was particularly hard-hit. It took 100 million years for the remaining species to recover from this extinction, nicknamed “The Great Dying”, and we are very lucky that life recovered at all.

So what caused the Permian-Triassic extinction? After the discovery of the K-T crater, many scientists assumed that impact events were a prerequisite for extinctions, but that probably isn’t the case. We can’t rule out the possibility that an asteroid aggravated existing conditions at the end of the Permian period. However, over the past few years, scientists have pieced together a plausible explanation for the Great Dying. It points to a trigger that is quite disturbing, given our current situation – global warming from greenhouse gases.

In the late Permian, a huge expanse of active volcanoes existed in what is now Siberia. They covered 4 million square kilometres, which is fifteen times the area of modern-day Britain (White, 2002). Over the years, these volcanoes pumped out massive quantities of carbon dioxide, increasing the average temperature of the planet. However, as the warming continued, a positive feedback kicked in: ice and permafrost melted, releasing methane that was previously safely frozen in. Methane is a far stronger greenhouse gas than carbon dioxide – over 100 years, it traps approximately 21 times more heat per molecule (IPCC AR4). Consequently, the warming became much more severe.

When the planet warms a lot in a relatively short period of time, a particularly nasty condition can develop in the oceans, known as anoxia. Since the polar regions warm more than the equator, the temperature difference between latitudes decreases. As global ocean circulation is driven by this temperature difference, ocean currents weaken significantly and the water becomes relatively stagnant. Without ocean turnover, oxygen doesn’t get mixed in – and it doesn’t help that warmer water can hold less oxygen to begin with. As a result of this oxygen depletion, bacteria in the ocean begins to produce hydrogen sulfide (H2S). That’s what makes rotten eggs smell bad, and it’s actually poisonous in large enough quantities. So if an organism wasn’t killed off by abrupt global warming, and was able to survive without much oxygen in the ocean (or didn’t live in the ocean at all), it would probably soon be poisoned by the hydrogen sulfide being formed in the oceans and eventually released into the atmosphere.

The Permian-Triassic extinction wasn’t the only time anoxia developed. It may have been a factor in the Late Triassic extinction, as well as smaller extinctions between the Big Five. Overall, it’s one reason why a warm planet tends to be less favourable to life than a cold one, as a 2008 study in the UK showed. The researchers examined 520 million years of data on fossils and temperature reconstructions, which encompasses almost the entire history of multicellular life on Earth. They found that high global temperatures were correlated with low levels of biodiversity (the number of species on Earth) and high levels of extinction, while cooler periods enjoyed high biodiversity and low extinction.

Our current situation is looking worse by the minute. Not only is the climate changing, but it’s changing in the direction which could be the least favourable to life. We don’t have volcanic activity anywhere near the scale of the Siberian Traps, but we have a source of carbon dioxide that could be just as bad: ourselves. And worst of all, we could prevent much of the coming damage if we wanted to, but political will is disturbingly low.

How bad will it get? Only time, and our decisions, will tell. A significant number of the world’s species will probably become extinct. It’s conceivable that we could cause anoxia in the oceans, if we are both irresponsible and unlucky. It wouldn’t be too hard to melt most of the world’s ice, committing ourselves to an eventual sea level rise in the tens of metres. These long-range consequences would take centuries to develop, so none of us has to worry about experiencing them. Instead, they would fall to those who come after us, who would have had no part in causing – and failing to solve – the problem.


Mayhew et al (2008). A long-term association between global temperature and biodiversity, origination and extinction in the fossil record. Proceedings of the Royal Society: Biological Sciences, 275: 47-53. Read online

Twitchett (2006). The paleoclimatology, paleoecology, and paleoenvironmental analysis of mass extinction events. Paleogeography, Paleoclimatology, Paleoecology, 234(2-4): 190-213. Read online

White (2002). Earth’s biggest “whodunnit”: unravelling the clues in the case of the end-Permian mass extinction. Philosophical Transactions of the Royal Society: Mathematical, Physical, & Engineering Sciences, 360: 2963-2985. Read online

Benton and Twitchett (2003). How to kill (almost) all life: the end-Permian extinction event. Trends in Ecology & Evolution, 18(7): 358-365. Read online

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Cross-posted from NextGen Journal

A few years ago, climate change mitigation became a major political issue. Before 2005, governments certainly knew that human-caused climate change was a serious problem – but the public knew next to nothing about it, so there was no incentive to act. However, between 2005 and 2007, a perfect storm of events splashed the reality of climate change onto the world stage.

The Kyoto Protocol, an international agreement to reduce greenhouse gas emissions, finally came into force in early 2005, after years of negotiation. The United States refused to sign, and Australia signed on a little late, but every other developed nation in the world agreed to emission targets. Here in Canada, the Liberal government enthusiastically pledged its support for Kyoto. My local newspaper ran editorials exploring the different ways we could meet our targets, through combinations of clean energy, green infrastructure, and efficiency standards.

The summer of 2005 was a wake-up call for the United States, as Hurricane Katrina mercilessly demonstrated the amount of damage that extreme weather can bring. It’s impossible to say, at least with our current technology, whether or not Katrina was caused or even worsened by a warming planet. However, such devastating storms will become the norm as climate change progresses. Scientists aren’t sure whether or not hurricanes will become more frequent in a warming world, but the average hurricane is expected to become stronger and more damaging, and we are already beginning to see this rise in storm intensity. Katrina gave us an example of what we can expect from climate change – even if it wasn’t a direct effect in itself – and the world was shocked by the suffering that ensued.

2006 marked the release of An Inconvenient Truth, Al Gore’s Academy Award-winning documentary about climate change. For scientists studying climate, the film was an admirable, up-to-date example of science communication, albeit with a few minor errors and oversimplifications. However, for citizens new to the issue (I particularly remember my classmates in grade 9 social studies discussing the film), An Inconvenient Truth was a disturbing reality check – scarier than any horror movie, because it was real.

The major scientific event of 2007 was a drastic, unexpected drop in Arctic summer sea ice. That season’s melt was exacerbated by coincidental weather conditions, so the next years weren’t quite as bad, but the trend was still worrying, to say the least. The research community had assumed that summer ice would stick around for at least a century, but this timescale was soon halved and quartered as ice melt exceeded even the worst projections.

By 2007, lead-up to the 2008 US presidential election was underway, and political awareness of climate change was obvious. It was no surprise that Democrat Barack Obama had ambitious plans to cut greenhouse gas emissions, but even the Republicans seemed to be on board. During his time in office, George W. Bush had insisted that, since climate change could be natural, any mitigating action was not worth the economic risk. Republican presidential candidates seemed to realize that continuing to adopt this attitude would be political suicide. The most extreme example, John McCain, who would eventually win the Republican presidential nomination, had emissions targets only slightly less extensive than Obama’s. As he said in 2007,

The world is already feeling the powerful effects of global warming, and far more dire consequences are predicted if we let the growing deluge of greenhouse gas emissions continue, and wreak havoc with God’s creation…The problem isn’t a Hollywood invention nor is doing something about it a vanity of Cassandra like hysterics. It is a serious and urgent economic, environmental and national security challenge.

However, McCain, once an author of a bill designed to cut greenhouse gas emissions, would soon completely change his stance. By 2010, he was asserting that cap-and-trade legislation was unnecessary and carbon dioxide posed no harm to the American people. He even went so far as to question the political motivations of science he once wholly accepted:

I think [global warming is] an inexact science, and there has been more and more questioning about some of the conclusions that were reached concerning climate change. And I believe that everybody in the world deserves correct answers whether the scientific conclusions were flawed by outside influences. There’s great questions about it that need to be resolved.

The story of John McCain isn’t too surprising. Politicians frequently base their statements on public sentiment rather than personal opinion. They say what people want to hear, rather than what they truly believe is important. This aspect of our political system is depressing, but persistent. The real question, though, regards what changed public sentiment so quickly. Why did politicians like McCain feel compelled to denounce the importance of action on this problem, or even the existence of the problem itself? What happened since 2007 that made the pendulum swing so far in the other direction?

Strike one was the economy. The global recession that began in 2008 was the largest since the Great Depression, and concern for all other problems promptly went down the drain. It’s understandable for citizens to not worry about the environment when they don’t even have the means to feed and clothe their children properly. However, for governments to not realize the long-term economic implications of allowing climate change to continue, along with the potential job-creating benefits of a new energy economy, was disappointing, even though it wasn’t surprising.

Strike two was the all-out war on climate science, spearheaded by the fossil fuel industry and the far right. This PR campaign has been underway since the early 1990s, but was kicked up a notch just over a year ago. Since public understanding of the causes and effects of global warming was growing, and the science was becoming more solid by the month, the PR tactics changed. Instead of attacking the science, they attacked the integrity of the scientists. The most extreme example occurred in November 2009, when private correspondence between top climate researchers was stolen, spread on the Internet, and spun in an attempt to cast doubt on the scientists’ motives. This event, known as “Climategate”, spurred a great deal of anger among the political right, and everything from bitter editorials to death threats against scientists ensued. Perhaps most distressingly, by the time investigations found that the scientists involved were innocent, and the reality of climate change untouched, Climategate was old news and media outlets failed to adequately follow up on the story. Citizens heard the accusations, but not the exonerations, so political will to cut greenhouse gas emissions slipped even further.

Strike three – well, there has been no strike three, and a good thing too. Strikes one and two were so bad that some are hoping the pendulum has swung as far as it can go. It’s certainly difficult to imagine how the situation could get worse. The Kyoto Protocol is set to expire next year, and the Copenhagen meetings failed to create a replacement. As it was, many developed nations failed to meet their targets, and the Canadian government backed out completely.

The possibility of federal climate legislation for the United States is laughable now that not a single Republican Senator thinks action is necessary, and most doubt the reality of the problem, choosing to believe that the entire scientific community is out to lunch and/or an agent of conspiracy. President Obama’s director of climate policy, Carol Browner, recently left her position, although none of her major goals had been met. Obama’s recent State of the Union address included lots of hopeful statements about clean energy, but absolutely no mention of climate change, as if merely acknowledging the most pressing reason for a new energy economy would be political suicide. The time-honoured tradition of saying what the public wants to hear has even reached Obama, the man who promised change.

In Canada, legislation to simply set targets for emission reduction passed the House of Commons (made of elected representatives), but the Senate (composed of appointed politicians) chose to use their newfound Conservative majority to strike down the bill with no debate whatsoever, in a blatantly undemocratic move that has not happened since the 1930s. The Canadian government is all for a new energy economy, but not one based on environmental and social responsibility. The Alberta tar sands, which are substantially more polluting and carbon-intensive than traditional oil, continue to expand, and both federal and provincial governments are worryingly enthusiastic.

From 2005 to 2007, politics was high on promises of mitigation, but low on delivery. Since then, it has been devoid of both. It’s starting to seem as if it will take a major global disaster that can be unquestionably tied to climate change for governments to get their act together.

This would all be very well if there was no lag time between cause and effect in the climate system, but it doesn’t work that way. It takes several decades for all the warming in the pipeline to show up. If we waited until climate change became unbearable, and then cut off our emissions completely, the situation would still get worse for decades before it stabilized.

The worldwide failure of governments to take action on climate change is baffling. It seems that the best they can do is occasionally promise to fix the problem, but never actually get started. If this continues for much longer, we’re all going to pay the price for their mistakes – and so will people for generations to come.

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Cross-posted from NextGen Journal

As an aspiring climate scientist, I have read dozens of books about climate change over the past few years. Here are my all-time favourites, which I present with Unofficial Climate Change Book Awards. (Unfortunately, the prizes consist entirely of bragging rights.)

Best Analysis of Future Scenarios
Climate Wars, by Gwynne Dyer
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Most of us are aware of how climate change will impact the world: more extreme weather, prolonged floods and droughts, dwindling glaciers and sea ice. In this book, renowned Canadian journalist and military historian Gwynne Dyer goes one step further, and explores how these physical impacts might affect geopolitical relations. Will India and Pakistan engage in nuclear warfare over clean water? Will the United States and Russia begin a “Colder War” over Arctic sovereignty? Many of the scenarios he writes about are, frankly, terrifying, and all have a frightening grain of plausibility to them. Read the full review

Best Introduction to Climate Science
The Discovery of Global Warming, by Spencer Weart
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Scientists overwhelmingly agree that human-caused climate change is underway, but instead of simply stating this conclusion, Weart tells the story of how it was reached: tracing the theory from the 1800s to today. This innovative approach to science education, combined with Weart’s elegant prose, makes the book a joy to read. It doesn’t feel like a textbook, although it contains as much information as one. Read the full review

Best Exposé
Climate Cover-Up, by James Hoggan and Richard Littlemore
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If scientists are so sure about the reality of anthropogenic climate change, why does so much of the public think that it’s natural/nonexistent/a global conspiracy? Why does the media present the issue as an equal-sided scientific debate? This confusion didn’t just happen by accident – it was deliberately constructed. Over the past two decades, lobby groups representing industries or ideologies that seek to delay action on climate change have engaged in a campaign to spread doubt about the reality of the problem. This book, rather than throwing around baseless accusations, methodically examines the paper trail of this widespread campaign. Reading Climate Cover-Up is an infuriating but absolutely necessary journey to take. Read the full review

Best Policy Discussion
Storms of my Grandchildren, by Dr. James Hansen
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James Hansen is possibly the most prominent climate scientist alive today, and that title is well-deserved. Throughout his career at NASA, he has frequently made discoveries that were ahead of his time. Dr. Hansen is a very intrinsic scientist who doesn’t enjoy being in the spotlight or talking about policy, but he wrote this book for fear of his grandchildren looking back at his work and saying, “Opa understood what was happening, but he did not make it clear.” Although he couldn’t resist slipping in a few chapters about the current frontiers of climate science, the bulk of the book is about policy, featuring compelling arguments for expanded nuclear power, a moratorium on coal, and a rising price on carbon. Read the full review

Best Canadian Focus
Keeping Our Cool, by Dr. Andrew Weaver
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Andrew Weaver is Canada’s top climate modeller, and a fantastic role model for science communication. This book gives a high-level, yet accessible, explanation of the mathematics of climate change – if you have some basic knowledge of calculus and statistics, you should be fine. However, what really makes this book stand out is its focus on Canadian climate journalism and politics, a rare quality in a field dominated by American research. We all know about George W. Bush’s track record of inaction, but what has Prime Minister Stephen Harper done (or not done)? High-profile studies exist on American media coverage of global warming, but how does the Canadian press compare? Read the full review

Best Insider’s Account
Science as a Contact Sport, by Dr. Stephen Schneider
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The late Stephen Schneider, who unexpectedly died last summer of a heart attack, is a true pioneer of climate modelling. He has been active in the field since the 1970s, when computers became fast enough to handle mathematical models. This memoir explains what it’s like to be a climate scientist, and how that has changed over the years. In the 70s, Schneider and his colleagues filled their mind with purely analytical questions, but today, they have to deal with the media, politicians, and hate mail as well. Science used to just be about science, but now it’s about communication as well. Read the full review

Most Gripping
Snowball Earth, by Gabrielle Walker
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Gabrielle Walker is a brilliant woman, as she possesses the ability to make a book about geology every bit as gripping as a murder mystery. Granted, Snowball Earth, a recent theory of climatic conditions during the Precambrian Era, is fascinating. In short, the continents were arranged in such a manner that the Earth would swing back and forth between “Snowball Earth” (frozen oceans and frozen land all over, even at the Equator) and “Hothouse Earth” (massive global warming from volcanic emissions of carbon dioxide). Until this period of massive climatic swings, the only thing that lived on Earth was unicellular goop…but immediately following the Snowball Earth cycles, complex life appeared. Many scientists don’t think this evolutionary timing was a coincidence. It’s possible that multicellular organisms, including us, only exist because of an accident of plate tectonics. Read the full review

If you would like to contest any of my decisions for these awards, please feel free to do so in the comments!

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