The Sting of the Long Tail: Climate Change, Delayed Harm, and Backlash
In the comments to Ann’s earlier post, the question was raised as to why global temperatures haven’t declined in response to the decline in carbon dioxide emissions from Europe in the past year. I made a quick response to this question in the comments, but I wanted to elaborate on that response here. What follow is a brief summary of a recent article I wrote on the issue, which you can find here.
The basic problem is a common one in environmental law – there can be a substantial time lag between a human activity and the environmental harm from that human activity. In the context of climate change, this means that carbon dioxide emissions today don’t necessarily result in increased temperature on a global scale tomorrow – their full impact in fact won’t be felt for decades from now. The primary reason for this is the high heat capacity of water – as anyone who has tried to watch a pot of water boil knows, it takes a long time to heat up water (or reciprocally, cool it down). (This is also why oceans and lakes tend to moderate temperature swings in the areas around them.) In the context of climate change, this means that even as CO2 increases the atmospheric temperature, there will be a time delay (measured in decades) between when the rises in atmospheric temperatures connect to changes in the temperatures of the oceans. And because oceans are an important driver of the global climate system, this means that the full effects of CO2 emissions on the global climate won’t be manifested for decades as well. (We’ll also see extended delays in terms of when the full effects of CO2 emissions today will be felt in terms of sea level rise and ice sheet changes for similar reasons.)
This delay in harm from CO2 emissions has an important implication for any regulatory system for carbon emissions (whether it is a carbon tax, a cap-and-trade system, or a command-and-control system). Even if we terminated all CO2 emissions tomorrow (perhaps with a global “hold your breath week”), there would still be increases in global temperatures over a time frame of decades as a result of what scientists call “warming commitment” or “climate change commitment” – the changes in global climate that are already going to occur because of CO2 emissions in the past.
The comment to Ann’s post encapsulates perfectly the political problem that this is likely to create for any future carbon regulatory system. Whatever system we install to restrict carbon emissions, it will have no impact on the changes in global climate that are already destined to occur because of the emissions that have already happened. Those who are skeptical of anthropogenic climate change (such as the commenter) will undoubtedly seize on the continued change in global climate despite carbon regulation as “proof” that there is no connection between carbon emissions and global climate change. (They will be wrong, for the reasons given above.) Even those who are not skeptics might wonder if our regulatory efforts are really worth the trouble, if we’re still moving into unprecedented (in terms of human experience) changes in the environment regardless of our regulatory efforts, maybe we should emphasize adaptation much more than mitigation. Why spend a whole lot of time and energy to “save the planet” when it is changing anyway? In any case, one might expect a significant backlash against any carbon regulatory system in response to this delayed harm phenomenon.
One possible solution to this dilemma is to try and “undo” the harm that past carbon emissions have created. We can’t just wait for the CO2 in the atmosphere to disperse, even if we stop all emissions, because the residence time in the atmosphere is so long (1000+ years in the latest estimates). So we might be forced – for political reasons if nothing else – to consider various “geoengineering” schemes either to reduce the levels of CO2 in the atmosphere through active efforts to extract the CO2, or to offset the impacts of CO2 on the global climate system (one fashionable proposal is to use sulfur in the upper atmosphere to reduce the amount of sunlight that warms the planet, offsetting the impact of higher CO2 levels). Of course, these “geoengineering” strategies carry their own risks of side-effects, unexpected consequences, and tremendous ethical problems. But given the political problems that we might be facing, we might not have much of a choice.
Reader Comments
5 Replies to “The Sting of the Long Tail: Climate Change, Delayed Harm, and Backlash”
Comments are closed.
About Eric
Eric Biber is a specialist in conservation biology, land-use planning and public lands law. Biber brings technical and legal scholarship to the field of environmental law…
READ more
A more specific explanation of the continued temperature increase is that temperatures depend on atmospheric GHG concentrations, not emission rates. Emission rates have declined, but accumulated atmospheric GHG levels are still increasing (albeit at a somewhat slower rate).
Monbiot discussed this issue in one of his blogs some time ago ( http://www.monbiot.com/archives/2009/07/14/pulling-yourself-off-the-ground-by-your-whiskers/ ). See the second to the last paragraph: “Two recent papers in Nature show that the measure which counts is not the proportion of current emissions produced on a certain date, but the total amount of greenhouse gases we release …”
Certainly because of the long residence time of CO2 in the atmosphere, even reducing emissions significantly now will result in increasing CO2 concentrations in the atmosphere because it takes so long for the CO2 to be removed from the atmosphere. But even if we stopped all additional emissions, the existing greenhouse gas concentrations at the current level will result in additional temperature increases in the future. Both points make the delayed harm of CO2 hard to deal with, but the second point has not received much attention as a policy matter.
The connection between CO2 concentrations and atmospheric temperature remains a subject of scientific inquiry that is far from settled. CO2 is merely a trace gas which has a much smaller effect on climate than water vapor, natural cycles and solar radiation. There is no scientific proof that CO2 is the driving force in global warming. Likewise, there is no proof that small and insignificant reductions in anthropogenic emissions of CO2 would have any long term effect on atmospheric temperatures. Many good and rational citizens believe that we can safely dismiss futile proposals to regulate climate and it is encouraging to watch the retreat on this issue.
The second sentence in bqrq’s post is largely correct, though ‘merely’ seems a poor way to describe C02, an atmospheric component of such huge importance for the biosphere. I take it bq means “variation” in solar radiation.
None of that means that increased CO2 in the atmosphere won’t lead to higher temperatures. CO2 is opaque to infrared radiation across parts of the spectrum where water vapor is transparent, and one of those windows, near 12 micrometers, corresponds to the Earth’s peak thermal radiation.
The effect is relatively small–smaller than normal variation in solar radiation, for example–but all other things remaining equal over time, more CO2 means an increased greenhouse effect. NASA says the effect is equivalent to an additional solar input of 0.8 watt per square meter, a value difficult to measure against background variation or “noise”, but, none-the-less, very significant over time.
There are, of course, lots of complications–complications pretty much beyond my ken. For example, what is the interaction between increased temperature and water vapor in the atmosphere. Will clouds increase? Will clouds increase the greenhouse effect or increase the Earth’s albedo? What of the other changes man is making to the atmosphere and the planet? Pollution? Land use changes affecting vegetation and albedo.
Perhaps I’m wrong, but I feel the search for the temperature “smoking gun” is a distraction. Climate change is an energy balance problem and given the huge thermal inertia in the oceans and the ice caps, it’s going to be hard to tease temperature increases out of the data, even as the total heat in the system increases. Not to mention the extra energy that is converted to kinetic energy rather than heat. (How did all that heavy, cold polar air get to the temperate zones last December? That kind of thing usually happens in February, when the sun returns to the Arctic and stirs things up.)
Along those lines, one comment. The example above of water boiling is perhaps unfortunate. True, it takes a significant amount of heat to raise the temperature of water, but it takes a huge increase to send it through a phase change. If I remember correctly from 8th grade, it takes 30 x more energy to melt a gram of ice than it does to raise the temperature of a gram of water 1 degree. The factor for boiling is closer to 100.
As far as climate goes, the fact that water is relatively transparent is also really important. The sun heats much more of it, heats it to a much greater depth, relative to land. I think that is why, not so much the difference in specific heat, that coastal climates are milder.
There is a mistake (at least one) in my comment–the part about kinetic energy. The conversion of heat to kinetic energy would only be temporary, converting back to heat. (There might be some effect on convection that causes energy to exit the system.)
Nature abhors steep gradients. The temperature can only increase or fall so much in one place before things become unstable. Storms redistribute the heat, even things out.