Modelling Geoengineering

Later in my career as a climate modeller, I expect to spend a lot of time studying geoengineering. Given the near-total absence of policy responses to prevent climate change, I think it’s very likely that governments will soon start thinking seriously about ways to artificially cool the planet. Who will they come to for advice? The climate modellers.

Some scientists are pre-emptively recognizing this need for knowledge, and beginning to run simulations of geoengineering. In fact, there’s an entire model intercomparison project dedicated to this area of study. There’s only a small handful of publications so far, but the results are incredibly interesting. Here I summarize two recent papers that model solar radiation management: the practice of offsetting global warming by partially blocking sunlight, whether by seeding clouds, adding sulfate aerosols to the stratosphere, or placing giant mirrors in space. As an added bonus, both of these papers are open access.

A group of scientists from Europe ran the same experiment on four of the world’s most complex climate models. The simulation involved instantaneously quadrupling CO2 from preindustrial levels, but offsetting it with a reduction in the solar constant, such that the net forcing was close to zero.

The global mean temperature remained at preindustrial levels. “Great,” you might think, “we’re home free!” However, climate is far more than just one globally averaged metric. Even though the average temperature stayed the same, there were still regional changes, with cooling in the tropics and warming at both poles (particularly in their respective winters):

There were regional changes in precipitation, too, but they didn’t all cancel out like with temperature. Global mean precipitation decreased, due to cloud feedbacks which are influenced by sunlight but not greenhouse gases. There were significant changes in the monsoons of south Asia, but the models disagreed as to exactly what those changes would be.

This intercomparison showed that even with geoengineering, we’re still going to get a different climate. We won’t have to worry about some of the big-ticket items like sea level rise, but droughts and forest dieback will remain a major threat. Countries will still struggle to feed their people, and species will still face extinction.

On the other side of the Atlantic, Damon Matthews and Ken Caldeira took a different approach. (By the way, what is it about Damon Matthews? All the awesome papers out of Canada seem to have his name on them.) Using the UVic ESCM, they performed a more realistic experiment in which emissions varied with time. They offset emissions from the A2 scenario with a gradually decreasing solar constant. They found that the climate responds quickly to geoengineering, and their temperature and precipitation results were very similar to the European paper.

They also examined some interesting feedbacks in the carbon cycle. Carbon sinks (ecosystems which absorb CO2, like oceans and forests) respond to climate change in two different ways. First, they respond directly to increases in atmospheric CO2 – i.e., the fertilization effect. These feedbacks (lumped together in a term we call beta) are negative, because they tend to increase carbon uptake. Second, they respond to the CO2-induced warming, with processes like forest dieback and increased respiration. These feedbacks (a term called gamma) are positive, because they decrease uptake. Currently we have both beta and gamma, and they’re partially cancelling each other out. However, with geoengineering, the heat-induced gamma goes away, and beta is entirely unmasked. As a result, carbon sinks became more effective in this experiment, and sucked extra CO2 out of the atmosphere.

The really interesting part of the Matthews and Caldeira paper was when they stopped the geoengineering. This scenario is rather plausible – wars, recessions, or public disapproval could force the world to abandon the project. So, in the experiment, they brought the solar constant back to current levels overnight.

The results were pretty ugly. Global climate rapidly shifted back to the conditions it would have experienced without geoengineering. In other words, all the warming that we cancelled out came back at once. Global average temperature changed at a rate of up to 4°C per decade, or 20 times faster than at present. Given that biological, physical, and social systems worldwide are struggling to keep up with today’s warming, this rate of change would be devastating. To make things worse, gamma came back in full force, and carbon sinks spit out the extra CO2 they had soaked up. Atmospheric concentrations went up further, leading to more warming.

Essentially, if governments want to do geoengineering properly, they have to make a pact to do so forever, no matter what the side effects are or what else happens in the world. Given how much legislation is overturned every time a country has a change in government, such a promise would be almost impossible to uphold. Matthews and Caldeira consider this reality, and come to a sobering conclusion:

In the case of inconsistent or erratic deployment (either because of shifting public opinions or unilateral action by individual nations), there would be the potential for large and rapid temperature oscillations between cold and warm climate states.

Yikes. If that doesn’t scare you, what does?

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Climate Change and Heat Waves

One of the most dangerous effects of climate change is its impact on extreme events. The extra energy that’s present on a warmer world doesn’t distribute itself uniformly – it can come out in large bursts, manifesting itself as heat waves, floods, droughts, hurricanes, and tornadoes, to name a few. Consequently, warming the world by an average of 2 degrees is a lot more complicated than adding 2 to every weather station reading around the world.

Scientists have a difficult time studying the impacts of climate change on extreme events, because all these events could happen anyway – how can you tell if Hurricane Something is a direct result of warming, or just a fluke? Indeed, for events involving precipitation, like hurricanes or droughts, it’s not possible to answer this question. However, research is advancing to the point where we can begin to attribute individual heat waves to climate change with fairly high levels of confidence. For example, the recent extended heat wave in Texas, which was particularly devastating for farmers, probably wouldn’t have happened if it weren’t for global warming.

Extreme heat is arguably the easiest event for scientists to model. Temperature is one-dimensional and more or less follows a normal distribution for a given region. As climate change continues, temperatures increase (shifting the bell curve to the right) and become more variable (flattening the bell curve). The end result, as shown in part (c) of the figure below, is a significant increase in extremely hot weather:

Now, imagine that you get a bunch of weather station data from all across the world in 1951-1980, back before the climate had really started to warm. For every single record, find the temperature anomaly (difference from the average value in that place and on that day of the year). Plot the results, and you will get a normal distribution centred at 0. So values in the middle of the bell curve – i.e., temperatures close to the average – are the most likely, and temperatures on the far tails of the bell curve – i.e. much warmer or much colder than the average – are far less likely.

As any statistics student knows, 99.7% of the Earth’s surface should have temperatures within three standard deviations of the mean (this is just an interval, with length dependent on how flat the bell curve is) at any given time. So if we still had the same climate we did between 1951 and 1980, temperatures more than three standard deviations above the mean would cover 0.15% of the Earth’s surface.

However, in the past few years, temperatures three standard deviations above average have covered more like 10% of the Earth’s surface. Even some individual heat waves – like the ones in Texas and Russia over the past few years – have covered so much of the Earth’s surface on their own that they blow the 0.15% statistic right out of the water. Under the “old” climate, they almost certainly wouldn’t have happened. You can only explain them by shifting the bell curve to the right and flattening it. For this reason, we can say that these heat waves were caused by global warming.

Here’s a graph of the bell curves we’re talking about, in this case for the months of June, July, and August. The red, yellow and green lines are the old climate; the blue and purple lines are the new climate. Look at the area under the curve to the right of x = 3: it’s almost nothing beneath the old climate, but quite significant beneath the new climate.

Using basic statistical methods, it’s very exciting that we can now attribute specific heat waves to climate change. On the other hand, it’s very depressing, because it goes to show that such events will become far more likely as the climate continues to change, and the bell curve shifts inexorably to the right.

References:

A Conversation with Gavin Schmidt

Cross-posted from NextGenJournal

Dr. Gavin Schmidt is a climate modeller at NASA’s Goddard Institute for Space Studies, as well as the editor at RealClimate. I recently had the opportunity to interview Dr. Schmidt, one of the top scientists in his field, on what we can expect from the climate in the coming decades. Here is the entirety of the interview we completed for my article Climate Change and Young People.

Kate: In a business-as-usual scenario, what range of warming can we expect within the lifetimes of today’s young people – so to about 2070 or 2080?

Gavin: Well, we don’t have a perfect crystal ball for exactly what “business-as-usual” means, but the kind of projections that people have been looking at – which involve quite high increases in population and minimal changes in technology – you are talking about global temperature changes, by about 2070, of somewhere between two, three, five degrees Celsius, depending a little bit on the scenario, and a little bit on how sensitive the climate actually is.

That metric is a bit abstract to most people, so how will that amount of warming actually impact people’s lives?

That’s a very good question, because most people don’t live in the global mean temperature, or the global mean anything. Those kinds of numbers translate to larger changes, between four and six degrees of warming, over the land. As you go towards the poles it becomes larger as well, because of the amplifying feedbacks of ice albedo changes and reductions in snow cover.

Right now the range between a cold summer and a warm summer, in most mid-latitude places, is on the order of a couple of degrees. You’ll be looking at summers then – the normal summer then – will be warmer than the warmest summers that you have now, and significantly warmer than the coldest summers. The same will be true in winter time and other seasons.

How will that impact metrics such as agriculture, food prices, the economy…?

It’s easy enough to say that there are going to be some impacts – obviously agriculture depends on the climate that exists. People will adapt to that, they’ll plant earlier, but crops are very sensitive to peak summer temperatures. So you’ll see losses in the fatally sensitive crops. But then you’ll see movement north of crops that were grown further south. You have to deal with the other changes – in nutrient balances, water availability, soil quality. We’re not talking about just moving the subtropics further toward the poles.

Lots of other things are going to change as well. Pests travel much faster with climate than do other kinds of species: invasive species tend to increase faster, because they’re moving into an empty niche, than species that are already well established. There’s going to be changes to rainfall regimes, whether it snows or rains, how heavily it rains – a lot of those things will tax infrastructure.

You’ve got changes for people living on the coast related to sea level rise. That will lead to changes in the damaging effects of storm surges when any particular storm comes through. We’re also looking at more subtle changes to the storms themselves, which could even amplify that effect.

How much of this warming, and these impacts, are now inevitable? Do we have the ability to prevent most of it, and what would that take?

Some further changes are inevitable. The system has so much inertia, and it hasn’t even caught up with what we’ve put into the atmosphere so far. As it continues to catch up, even if we don’t do anything else to the atmosphere from now on, we’ll still see further warming and further changes to the climate. But we do have a choice as to whether we try and minimize these changes in the future, or we allow the maximum change to occur. And the maximum changes really are very large. It’s been said that if we allow that to happen, we’ll end up living on a different planet, and I think there’s some certain truth to that.

I hear you talking a lot about uncertainty, and that’s something a lot of people are paralyzed by: they don’t want us to take these actions because they think everything might be fine on its own. What’s your response to that attitude?

Any decision that you’re making now that has to do with the future is uncertain. We make decisions all the time: where to invest money, whether to buy a house – these things aren’t certain, and we still have to make decisions. The issue with climate is that no action is a decision in and of itself. That one is actually laden with far more uncertainty than if we actually try and produce energy more efficiently, try and use more renewables, adjust the way we live so that we have a more sustainable future. The uncertainty comes with what would happen if we don’t make a decision, and I find that to be the dominant uncertainty. But climate change is not unique in having to deal with decision making under uncertainty. All decisions are like that. It’s nothing special about climate change in that there’s uncertainty about what’s going to happen in the future. Any time we decide to do anything, there’s uncertainty about the future, yet we still manage to get out of bed in the morning.

Probably in response to this attitude, climate science has got a lot of bad press in the past couple years. What have your experiences been – what sort of reactions have there been to your research?

There are a lot of people, particularly in the US, who perceive the science itself – just describing what’s going on and why – as a threat to their interests. To my mind, knowing what’s going on in the planet and trying to understand why should just be information, it shouldn’t be a threat. But other people see it as a threat, and instead of dealing with either their perceptions or what the science actually means, they choose to attack the science and they choose to attack the scientists. Basically, you just have people adopting a “shoot the messenger” strategy, which plays well in the media. It doesn’t get us very far in terms of better understanding what’s going on. But it does add a sort of smokescreen to divert people’s attention from what the real issues are. That’s regrettable, but I don’t think it’s at all surprising.

And finally, are you at all optimistic about the future?

It depends on the day.

Climate Change and Young People

Cross-posted from NextGen Journal

What is the most important policy issue facing today’s young people? Climate change might not seem like an obvious contender, as it feels so distant. Indeed, the majority of impacts from global warming have yet to come. But the magnitude and extent of those impacts are being determined right now. Only today’s young people will still be around to witness the effects of today’s actions.

Many people see climate change as just another environmental issue that will only impact the polar bears and coral reefs. In fact, it’s far more wide-reaching than that. An increase of only a few degrees in average global temperature will affect human systems of all kinds: agriculture, public health, economics, and infrastructure, just to name a few.

Dr. Gavin Schmidt, a climate modeller at NASA’s Goddard Institute for Space Studies and one of the world’s top scientists studying global warming, says that significant changes in global temperature can be expected within the lifetimes of young people alive today – “somewhere between two, three, five degrees Celsius, depending a little bit on the scenario, and a little bit on how sensitive the climate actually is.” It might sound like a small change, until you look back at the history of the Earth’s climate and realize that the last ice age was only around 5 degrees Celsius cooler than today. Additionally, the rate of warming (which is the more important metric for the ability of species, including people, to adapt) is higher today than it has been at any time for at the least the past 55 million years. Human technology has far surpassed the natural forces in the climate system, to the point where significant future warming is inevitable. In fact, says Schmidt, the climate system “hasn’t even caught up with what we’ve put into the atmosphere so far. As it continues to catch up, even if we don’t do anything else to the atmosphere from now on, we’ll still see further warming and further changes to the climate.”

However, the future is still quite malleable. Two degrees of warming is bad, but five degrees is far worse, and the difference between the two ends of the spectrum will depend on what we decide to do about the problem. Since our emissions of greenhouse gases, especially carbon dioxide, are causing global warming, the solution is self-evident: cut our emissions, as quickly as we can reasonably do so. Implementing this solution is not so simple, as fossil fuels are currently highly integrated into the global economy. Luckily, free-market mechanisms exist which alter the price signals of fossil fuels to better reflect the damage they cause. A revenue-neutral carbon tax, which is offset by reductions in income taxes or paid back evenly to the public as a dividend, is one solution; a cap-and-trade program, which treats carbon emissions like a currency, is another. While virtually nothing has been done in North America to cut emissions, the rest of the developed world has made a pretty good start.

Here in North America, the outlook for action is somewhat bleak. In the United States, says Schmidt, many people “perceive the science itself – just describing what’s going on and why – as a threat to their interests…they choose to attack the science and they choose to attack the scientists.” The Republican Party has adopted this strategy of denial, to the point where top presidential candidates such as Michelle Bachmann and Rick Perry truly believe that climate change is a hoax scientists cooked up to get grant money. The Democrats largely accept the science, but after nearly a full term in office, President Barack Obama hasn’t made any progress on the cap-and-trade program he promised upon his election. In Canada, Prime Minister Stephen Harper has repeatedly said that he will follow whatever actions the United States takes, or does not take, on climate change policy.

It seems that action necessary to mitigate global warming won’t be taken unless citizens demand it. Otherwise, emissions will likely continue unabated until the problem is too severe to ignore any longer – and even then, the situation will get worse for decades while the climate system catches up. “No action,” says Schmidt, “is a decision in and of itself.”

What decision, then, will we make? Will we get our act together in time to keep the warming at a tolerable level? Or will we choose to let it spiral out of control? Will future societies look back on us with resentment, or with admiration? Remember, you and I are part of those future societies. But we are also part of today’s.

Thousands of years from now, it won’t matter what the US deficit was in 2011, or which nations went to war with each other, or how much we invested in higher education. These issues matter a great deal to people today, but they are very transient, like many aspects of human systems. Climate change, though, will alter the earth on a geological timescale. It will take the planet around one hundred thousand years to undo what we are doing. We are leaving behind a very unfortunate legacy to the entirety of future human civilization, and all life on Earth – a legacy that is being shaped as you read this; a legacy that we could largely avoid if we chose to.

Harmony: a New Way of Looking at our World

Even if you don’t have any intention of reading the new book by Prince Charles of Wales, it’s almost worth buying a copy just to admire it. Harmony: a New Way of Looking at our World is beautifully bound, with thick, glossy pages full of photographs that take you on a visual journey of the natural and architectural wonders of the world. Some, like the two-page spread of a humpback whale breaching, are joyful; others, such as the carcass of a young albatross, its digestive tract stuffed with plastic debris, are distressing.

The actual contents of the book were unique, but compelling. Rather than focusing on a particular issue and discussing it in depth, Prince Charles swept through just about every discipline you’d find in a modern university – agriculture, anthropology, architecture, art…and that’s only the A’s. This broad approach could easily have fallen into confusing disconnect, but he managed to connect each subject with what he referred to as a “golden thread”: a philosophical principle emphasizing the importance of following patterns seen in nature, and not trying to overwhelm or conquer it.

This approach is not really a “new way of looking at the world”, as the subtitle proclaims – in fact, it predates the dominant practice of Western society. For example, among indigenous civilizations that have modestly endured for many thousands of years, “not one…considers itself to be a master of creation”. Compare that to today’s industrialized society, which is only a few centuries old, and already views nature as a huge machine composed of independent parts which we can tweak at our will, rather than as a complex, dynamic system.

Prince Charles makes both emotional and scientific arguments to support his message, but he emphasizes the emotional ones first. I found this framing to be a turnoff, especially in the first chapter, which began, “This is a call to revolution. The Earth…is losing its balance and we humans are causing this to happen,” and continued from there. I couldn’t really take this narrative seriously, as I hadn’t yet heard his rational arguments, so the opening seemed far too dramatized. Perhaps others will find the initial appeals to emotion more effective than graphs and citations, but I was not impressed by them.

The meat of the book, however, was far better. Prince Charles explored a wide array of fascinating subjects that never managed to bore me. From the mathematical relationships found in the biosphere, to the importance of agricultural crop diversity in a changing climate, to the fascinating stream of engineering known as biomimicry, to the history of Islamic architecture…they may seem unrelated, but in fact all lead back to the importance of sustainability, in every sense of the word, and the incredible wisdom and beauty that can be found in nature.

The major flaw of Harmony, in my opinion, was the frequency of Prince Charles’ self-promotion. It seemed like nearly every second page contained a sentence similar to “(this particular problem) is very significant…and that is why I decided to start (some charity) to address it.” I think it’s wonderful that such a powerful and prolific figure is supporting projects for sustainability, but a better approach would have been to include an appendix of his charities at the end of the book. That way, the writing would have been less about him, and more about what he had to say.

There were also some obvious errors in the book, more serious than simple typos. 22 does not follow 13 in the Fibonacci Sequence, and the tilt of the Earth’s axis is not 24.5º (at least not at present). I expect these errors will be fixed in future editions.

The text’s discussion of climate change was fairly standard – think Al Gore’s slideshow, condensed into a few pages – but nonetheless very accurate and effective. There were some brief forays into paleoclimate which I enjoyed, too. Climate change was not the focus of this book, it was instead presented as a piece of a larger picture, but I appreciated the clarity with which it was addressed.

Although the scientific side of my mind is hyper-vigilant when I read nonfiction, I can relate to the deep affinity and spirituality people feel for the natural world. Nothing builds a sense of kinship like being out in the wilderness and recognizing how much smarter other species can be, in their own ways, than human beings. Nothing feels quite as healing as the quiet awe that strikes when a deer steps out onto the path ahead, or the joy and laughter that inevitably follow from watching songbirds. Nothing builds acceptance of the phenomenon of death like witnessing its omnipresence and necessity in any functioning ecosystem.

We could fill libraries with the economic, scientific, and health benefits of preserving nature in all its integrity. When it comes down to it, though, nature keeps us sane in the crazy world we have created for ourselves, and these emotional reasons are just as strong, if not stronger.