The Global Economic Impact of Climate Change

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Yale economist William Nordhaus has done some of the best research on the economic effects of climate change. In a new working paper, Nordhaus and Andrew Moffat survey the literature (27 studies) and look at 36 different estimates regarding the global economic impact of climate change by 2100. They note that the IPCC stated in their 2007 report, “Global mean losses could be 1 to 5% of GDP for 4°C of warming” (pg. 2). Overall, “there are many studies of theoretical temperature increases in the 2 to 4 °C range, and that they cluster in the range of a loss of 0 to 4% of global output” (pg. 13). The authors’ own “preferred regression” provides an “estimated impact” of “1.63 % of income at 3 °C warming and 6.53% of income at a 6 °C warming. We make a judgmental adjustment of 25% to cover unquantified sectors…With this adjustment, the estimated impact is -2.04 (+ 2.21) % of income at 3 °C warming and -8.16 (+ 2.43) % of income at a 6 °C warming” (pg. 3).

This supports my previous posts about the economics of climate change. Once again, climate change will drastically reduce income over the next 100 years without intervention (and recent research suggests that we might have more time to intervene than previously thought). But people will still be be significantly better off compared to us today even if we fail to act. They just won’t be as well off as they could have been.

The Effects of Climate Change on the U.S. Economy

Climate change could have massive negative effects on the U.S. economy according to a new study:

We exploited random fluctuations in seasonal temperatures across years and states, using the richness of historical data available in the US. We employed a panel regression framework with the growth rate of gross state product (GSP) and average seasonal temperatures for each US state, and found that summer and autumn temperatures have opposite effects on economic growth. An increase in the average summer temperature negatively affects the growth rate of GSP. An increase in the autumn temperature positively affects this growth rate, although to a lesser extent. This suggests that previous studies’ aggregation of temperature data into annual temperature averages may mask the heterogeneous effects of different seasons.

The summer effect is particularly pronounced in data since 1990. This leads to a negative net economic effect of rising temperatures. This implies that the US economy is still sensitive to temperature increases, despite the adoption of adaptive technologies such as air conditioning (Barreca et al. 2015). Temperature also has a stronger effect in states with relatively high summer temperatures, most of which are located in the south.

Our analysis quantified the effect of rising temperatures across sectors of the US economy. We find that an increase in average summer temperature has a pervasive effect on all industries, not just the sectors that are traditionally assumed to be vulnerable to climate change…In our empirical analysis, an increase in the average summer temperature decreased the annual growth rate of labour productivity. An increase in the average autumn temperature had the opposite effect. Our analysis used data at the macroeconomic level, but it is consistent with existing studies of this relationship at the microeconomic level (Zivin and Neidell 2014, Cachon et al. 2012, Zivin et al. 2015).

The authors find that the long-term effect of climate change would be a reduction in “the growth rate of US output by 0.2 to 0.4 percentage points by the end of the century. At the historical growth rate of US GDP of 4% per year, this would correspond to a reduction of up to 10%. The results are even more dramatic in the high emissions scenario (A2). Here, the reduction of economic growth could reach 1.2 percentage points, corresponding to roughly one-third of the historical annual growth rate of the US economy.”

You can see economist Bridget Hoffman explain the findings below:

These results echo Joseph Heath’s analysis of climate change’s effects on the global economy. But perhaps more important, it helps drive home his main point: climate change will drastically reduce economic growth over the next 100 years without intervention. But people will still be be significantly better off compared to us today even if we fail to act (check the GDP graph at about 0:46). They just won’t be as well off as they could have been.

Policy makers should consider both of these facts when discussing how to combat climate change.

Climate Change and Economic Growth

Philosopher Joseph Heath has an enlightening working paper on the economics and ethics of climate change. Heath is emphatic that his goal is

not to make a case for the importance of economic growth, but merely to expose an inconsistency in the views held by many environmental ethicists. Part of my reason for doing so is to narrow the gap somewhat, between the discussion about climate change that occurs in philosophical circles and the one that is occurring in policy circles, about the appropriate public response to the crisis. One of the major differences is that the policy debate is conducted under the assumption of ongoing economic growth, as well as an appreciation of the importance of growth for raising living standards in underdeveloped countries. The philosophical discussion, on the other hand, is dominated by the view that ongoing economic growth is either impossible or undesirable, leading to widespread acceptance of the steady-state view. This view is, however, a complete non-starter as far as the policy debate is concerned, because it is too easily satisfied. As a result, its widespread acceptance among philosophers (and environmentalists) has led to their large-scale self-marginalization (pg. 31).

Drawing on the economic research of economists Nicholas Stern and William Nordhaus, Heath proceeds to point out how misleading language often distorts and exaggerates the negative impact of climate change:

Stern adopts a similar mode of expression when he suggests that “in the baseline-climate scenario with all three categories of economic impact, the mean cost to India and South-East Asia is around 6% of regional GDP by 2100, compared to a global average of 2.6%.” The casual reader could be forgiven for thinking that the reference, when he speaks of “loss in GDP per capita,” is to present GDP. What he is talking about, however, is actually the loss of a certain percentage of expected future GDP. In some cases, he states this more clearly: “The cost of climate change in India and South East Asia could be as high as 9- 13% loss in GDP by 2100 compared with what could have been achieved in a world without climate change.” The last clause is of course crucial – under this scenario, GDP will not be 9-13% lower than it is right now, but rather lower than it might have been, in 2100, had there not been any climate change…In other words, what Stern is saying is that climate change stands poised to depress the rate of growth. This type of ambiguity has unfortunately become common in the literature. An important recent paper in Nature by Marshall Burke, Solomon M. Hsiang and Edward Miguel, estimating the anticipated costs of climate change, presents its conclusions in the same misleading way. The abstract of the paper states that “unmitigated climate change is expected to reshape the global economy by reducing average global incomes by roughly 23% by 2100.” The paper itself, however, states the finding in a slightly different way: “climate change reduces projected global output by 23% in 2100, relative to a world without climate change.” Again, that last qualifying clause is crucial, yet it was the unqualified version of the claim found in the abstract that made its way into the headlines, when the study was published (pgs. 15-16).

Heath acknowledges that

these potential losses are enormous, and they call for a strong policy response in the present. At the same time, what these economists are describing is not a “broken world,” in which “each generation is worse off than the last.” On the contrary, they are describing a world in which the average person is vastly better off than the average person is now – just not as well off as he or she might have been, had we been less profligate in our greenhouse gas emissions. It is important, in this context to recall that annual rate of real per capita GDP growth in India, at the time of writing is 6.3%, and so what Stern is describing is, at worst, the loss of approximately two years worth of growth. At the present rate of growth, living standards of the average person in India are doubling every 12 years. There are fluctuations from year to year, but the mean expectation of several studies, calculated by William Nordhaus, suggests that the GDP of India will be about 40 times larger in 2100 than it was in the year 2000 (which implies an average real growth rate of 3.8%). The 9-13% loss, due to climate change, is calculated against the 40-times-larger 2100 GDP, not the present one (pg. 16-17).

The full paper has more details and additional arguments. But this is the kind of serious cost/benefit analysis we need to be having about climate change.

The Real War on Science


New York Times reporter and best-seller John Tierny published an excellent article with City Journal in which he argues that the Left has waged a far more damaging and effective war on science than the Right, despite narratives to the contrary. The whole article is worth reading, but among his examples include:

  1. Extensive confirmation bias (and other biases) in the social sciences that result in skewed research, particularly regarding research comparing left-wing people and right-wing people.
  2. Taboos against valid research: for example, discouraging or outright condemning research that (a) explores genetic differences between genders or races (unless the genetic differences relate to differences in sexual orientation) or (b) finds negative impacts of single-parent households, LGBT parenting, or putting children in childcare versus stay-at-home parenting.
  3. Politicizing (and thus corrupting) research on (a) genetics and animal breeding (contributing to the eugenics movement of the early 20th century),  (b) overpopulation (contributing, Tierny argues, to China’s immoral and disastrous one-child policy), (c) environmental science (contributing to many different problems, such as increased death tolls from malaria when DDT was restricted or the spread of dengue and Zika virus due to needless fears of insecticides), and (d) food science (pushing low fat diets and greatly increasing American consumption of carbohydrates).

Tierny argues that possibly one of the greatest casualties of the Left’s war on science is the reputation of scientists. As he puts it: “Bad research can be exposed and discarded, but bad reputations endure.”

The whole article is worth reading, but here is a sampling:

In a classic study of peer review, 75 psychologists were asked to referee a paper about the mental health of left-wing student activists. Some referees saw a version of the paper showing that the student activists’ mental health was above normal; others saw different data, showing it to be below normal. Sure enough, the more liberal referees were more likely to recommend publishing the paper favorable to the left-wing activists. When the conclusion went the other way, they quickly found problems with its methodology.


The narrative that Republicans are antiscience has been fed by well-publicized studies reporting that conservatives are more close-minded and dogmatic than liberals are. But these conclusions have been based on questions asking people how strongly they cling to traditional morality and religion—dogmas that matter a lot more to conservatives than to liberals. A few other studies—not well-publicized—have shown that liberals can be just as close-minded when their own beliefs, such as their feelings about the environment or Barack Obama, are challenged.

Social psychologists have often reported that conservatives are more prejudiced against other social groups than liberals are. But one of Haidt’s coauthors, Jarret Crawford of the College of New Jersey, recently noted a glaring problem with these studies: they typically involve attitudes toward groups that lean left, like African-Americans and communists. When Crawford (who is a liberal) did his own study involving a wider range of groups, he found that prejudice is bipartisan. Liberals display strong prejudice against religious Christians and other groups they perceive as right of center.

Conservatives have been variously pathologized as unethical, antisocial, and irrational simply because they don’t share beliefs that seem self-evident to liberals. For instance, one study explored ethical decision making by asking people whether they would formally support a female colleague’s complaint of sexual harassment. There was no way to know if the complaint was justified, but anyone who didn’t automatically side with the woman was put in the unethical category. Another study asked people whether they believed that “in the long run, hard work usually brings a better life”—and then classified a yes answer as a “rationalization of inequality.” Another study asked people if they agreed that “the Earth has plenty of natural resources if we just learn how to develop them”—a view held by many experts in resource economics, but the psychologists pathologized it as a “denial of environmental realities.”


For his part, Holdren [a previous advocate of forced population control in the U.S.] has served for the past eight years as the science advisor to President Obama, a position from which he laments that Americans don’t take his warnings on climate change seriously. He doesn’t seem to realize that public skepticism has a lot to do with the dismal track record of himself and his fellow environmentalists. There’s always an apocalypse requiring the expansion of state power. The visions of global famine were followed by more failed predictions, such as an “age of scarcity” due to vanishing supplies of energy and natural resources and epidemics of cancer and infertility caused by synthetic chemicals. In a 1976 book, The Genesis Strategy, the climatologist Stephen Schneider advocated a new fourth branch of the federal government (with experts like himself serving 20-year terms) to deal with the imminent crisis of global cooling. He later switched to become a leader in the global-warming debate.


Yet many climate researchers are passing off their political opinions as science, just as Obama does, and they’re even using that absurdly unscientific term “denier” as if they were priests guarding some eternal truth. Science advances by continually challenging and testing hypotheses, but the modern Left has become obsessed with silencing heretics. In a letter to Attorney General Loretta Lynch last year, 20 climate scientists urged her to use federal racketeering laws to prosecute corporations and think tanks that have “deceived the American people about the risks of climate change.” Similar assaults on free speech are endorsed in the Democratic Party’s 2016 platform, which calls for prosecution of companies that make “misleading” statements about “the scientific reality of climate change.” A group of Democratic state attorneys general coordinated an assault on climate skeptics by subpoenaing records from fossil-fuel companies and free-market think tanks, supposedly as part of investigations to prosecute corporate fraud. Such prosecutions may go nowhere in court—they’re blatant violations of the First Amendment—but that’s not their purpose. By demanding a decade’s worth of e-mail and other records, the Democratic inquisitors and their scientist allies want to harass climate dissidents and intimidate their donors.


Related reading:


It’s Not Easy Being [A] Green [Planet]

As reported by NASA:

From a quarter to half of Earth’s vegetated lands has shown significant greening over the last 35 years largely due to rising levels of atmospheric carbon dioxide, according to a new study published in the journal Nature Climate Change on April 25.

An international team of 32 authors from 24 institutions in eight countries led the effort, which involved using satellite data from NASA’s Moderate Resolution Imaging Spectrometer and the National Oceanic and Atmospheric Administration’s Advanced Very High Resolution Radiometer instruments to help determine the leaf area index, or amount of leaf cover, over the planet’s vegetated regions. The greening represents an increase in leaves on plants and trees equivalent in area to two times the continental United States.

…However, carbon dioxide fertilization isn’t the only cause of increased plant growth—nitrogen, land cover change and climate change by way of global temperature, precipitation and sunlight changes all contribute to the greening effect. To determine the extent of carbon dioxide’s contribution, researchers ran the data for carbon dioxide and each of the other variables in isolation through several computer models that mimic the plant growth observed in the satellite data.

Results showed that carbon dioxide fertilization explains 70 percent of the greening effect, said co-author Ranga Myneni, a professor in the Department of Earth and Environment at Boston University. “The second most important driver is nitrogen, at 9 percent. So we see what an outsized role CO2 plays in this process.”

The surprising benefits of global warming.

Climate Change: A Political Question

The Economist has a short piece on climate change and politics that is as obvious as it is interesting. The partisan divide on climate change began in 1997 “when a Democratic president, Bill Clinton, threw his weight behind the UN effort to introduce mandatory caps for greenhouse-gas emissions.” Political support of science often has nothing to do with scientific literacy (as the Cultural Cognition Project at Yale has demonstrated). “Knowledge of science makes little difference to people’s beliefs about climate change,” the article states, “except that it makes them more certain about what they believe. Republicans with a good knowledge of science are more sceptical about global warming than less knowledgeable Republicans.” Climate change also seems to a concern of the privileged: “The rich are more concerned about climate change than the poor, who have many other things to worry about. A giant opinion-gathering exercise carried out by the United Nations finds that people in highly developed countries view climate change as the tenth most important issue out of a list of 16 that includes health care, phone and internet access, jobs, political freedom and reliable energy. In poor countries—and indeed in the world as a whole—climate change comes 16th out of 16.”

What is perhaps most interesting is that despite the gaps in percentage, the trends tend to be the same for Republicans, Independents, and Democrats.

Scientific Skepticism

Turns out Bill Nye isn’t entirely fond of GMOs:

I stand by my assertions that although you can know what happens to any individual species that you modify, you cannot be certain what will happen to the ecosystem.

Also, we have a strange situation where we have malnourished fat people. It’s not that we need more food. It’s that we need to manage our food system better.

So when corporations seek government funding for genetic modification of food sources, I stroke my chin.

Yet even though I’m in favor of GMOs, I think he’s perfectly fine signalling caution about the difficulty of studying cause/effect within whole ecosystems and potential political/corporate interests in science. As scientists and engineers, we should always be questioning how our theories and models can be inaccurate or inadequate, and as human beings, we should always be wary of outside influences on science. Yet by Bill Nye’s own standards, he’s a denier. There are no studies to indicate environmental problems with GMOs, and if the amount of corporate and political influence in GMOs worries Bill Nye, he should be equally suspicious about climate change.

As a practicing engineer, this is what drives me bonkers about many supposed science advocates who brook no dissent on their chosen topics. You either find out that they have little known reservations about other topics where the science is “clear” (like Bill Nye), or they have zero reservations or skepticism about anything scientific consensus says, in which case they are professing the most anti-scientific belief possible (like Neil DeGrasse Tyson). The heart of science is realizing that all theories are provisional, that at best our theories can be well attested, never absolutely proven true. Karl Popper, the famous philosopher of science, believed that:

Scientific theories…are not inductively inferred from experience, nor is scientific experimentation carried out with a view to verifying or finally establishing the truth of theories; rather, all knowledge is provisional, conjectural, hypothetical—we can never finally prove our scientific theories, we can merely (provisionally) confirm or (conclusively) refute them; hence at any given time we have to choose between the potentially infinite number of theories which will explain the set of phenomena under investigation. Faced with this choice, we can only eliminate those theories which are demonstrably false, and rationally choose between the remaining, unfalsified theories. Hence Popper’s emphasis on the importance of the critical spirit to science—for him critical thinking is the very essence of rationality. For it is only by critical thought that we can eliminate false theories, and determine which of the remaining theories is the best available one, in the sense of possessing the highest level of explanatory force and predictive power.

I suppose people will now want to know what I believe about climate change, or conversely, if I say nothing people will probably start assuming. I know the earth is warming up. That’s not very hard to measure. I know that humans contribute to that warming. Again, not very hard to measure nor controversial. I do not know, though, to what extent humans contribute to the warming, nor to what extent reducing our greenhouse gas output a reasonable amount would actually slow this warming. That’s where the science of the matter gets difficult, because now we’re dealing with a whole ecosystem (like with GMOs), and sussing out cause and effect in a whole ecosystem is tricky. So currently, I have no strong opinion one way or the other. We could be contributing greatly to warming. Or our input could be modest. Modeling these effects and predicting warming rates is finicky to say the least.

Then when we get to the politics and economics of global warming, the situation is even messier. Will carbon taxes actually reduce greenhouse gas output in any significant amount worth the economic costs? Can we even reduce our greenhouse gas output any appreciable amount that won’t send the American public into shock? This is where global warming gets beyond my expertise.

So generally I just support measures that benefit us anyways with the side effect of combating greenhouse gas output. I support monitoring and regulating pollution output. I support continuing research into alternative energy sources, which isn’t just solar and wind for the record. We have geothermal, hydroelectric, wave energy, biomass, and more. I realize many of these methods are limited in their production capacity, location, and reliability, but they are capable of producing power amounts that aren’t insignificant.

More importantly, I support nuclear power, which has none of the above limitations. Now this is where all the talk about supporting science gets really odd. Nuclear power plants have a very good safety record (despite what the news says), and engineers are constantly working to make them better. On top of that, add the context of nuclear safety versus other sources of power. On top of that, add some perspective on radiation amounts (yes I cited XKCD). On top of that, add the oft cited dire effects of global warming. In that context, how can opposing nuclear power be anything short of anti-scientific and ridiculous, using the vocabulary abundant in discussion of global warming? And yet, people do it. Many climate scientists are jumping on board the nuclear train, but there’s still plenty of opposition. People proclaim the inviolability of scientific consensus in one context and then turn around to challenge it in a different context.

So, what general principles can we derive from this long-winded analysis? I would say people need to be able to simultaneously hold two seemingly contradictory concepts in their mind: Science is a quest for understanding the natural world, and science can never finally prove anything. With that knowledge, we should respect the explanatory power of science but also realize that science relies fundamentally on a critical spirit. We cannot crush dissent, nor should set ourselves up as arbiters of what constitutes “valid” dissent, which is really just crushing dissent by a different name. Rather, we must continually attempt to falsify our own theories, and if they survive the continuing ordeals, we can begin to call them well attested. But even then we must not close our minds, even as we defend theories we believe to be well attested. Newtonian physics reigned 300 years before general relativity showed up.

How do these principles look practically? I would say they manifest themselves in simultaneously laying down what we know while maintaining a spirit of humility. For example, I have defended evolution numerous times contra creationism. I don’t resort to telling people they’re scientifically illiterate (even though people who try to tell a chemical engineer how the 2nd law of thermodynamics “actually” works might qualify). I don’t demand they accept the consensus of science over their doubts (which would be horrifically anti-scientific). Rather, I just tell them what I know and demonstrate the explanatory power of evolution. You’d be surprised how well that works. Even if people don’t change their minds right then and there, it gets their minds thinking, and it allays their fears that I have an ulterior motive for defending evolution.

I believe these principles would serve science advocacy well. There is no contradiction between lacking absolute certainty and seeking scientific knowledge. In fact, the two work together. By realizing our own limitations, we can continually revise our understanding to better reflect what we see and what we know of the natural world. To say that we have finally and definitively figured out the answers ends the scientific quest and permanently extinguishes the scientific spirit.

Shaky Global Warming Models

2014-10-29 Global Warming

Earlier this month the Wall Street Journal ran an opinion piece by Dr. Judith Curry, former chairwoman of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology and the President of the Climate Forecast Applications Network. The gist of the article is simple: global warming predictions based on current models are predicting unrealistically high levels of climate change. The real levels–based on observational models–are much lower.

Continuing to rely on climate-model warming projections based on high, model-derived values of climate sensitivity skews the cost-benefit analyses and estimates of the social cost of carbon. This can bias policy decisions. The implications of the lower values of climate sensitivity in our paper, as well as similar other recent studies, is that human-caused warming near the end of the 21st century should be less than the 2-degrees-Celsius “danger” level for all but the IPCC’s most extreme emission scenario.

This slower rate of warming—relative to climate model projections—means there is less urgency to phase out greenhouse gas emissions now, and more time to find ways to decarbonize the economy affordably. It also allows us the flexibility to revise our policies as further information becomes available.

To me, this represents a moderate and mature approach to climate change. Curry’s work neither denies global warming nor the human factor in causing global warming. It simply suggests that climate models are biased upwards, and that we might have more time. Time that could be used to develop more sophisticated solutions to a post-carbon economy. This is really important given news like (just as an example) the announcement from Lockheed Martin that they are just 5 years away from a prototype nuclear fusion reactor.

I just finished reading Tim Flannery’s Here on Earth, which was the most eloquent and serious defense of the Gaia Hypothesis I’ve ever read, so I really  like the idea of greater human responsibility for our environment. I just think we’ll do a better job of living up to that responsibility if we have (1) a little less partisanship and (2) a deeper understanding of the relevant science. A little more time can help.

Dropping CO2 Emissions

Hank Campbell at Science 2.0 has a great post on natural gas and climate change. After noting that the IPCC reported that methane has 23x the global warming effect as CO2 (though CO2 lasts longer), Campbell mentions a couple recent studies “that methane will cause global warming regardless of CO2″:

What changed? Well, CO2 emissions went down, and it wasn’t due to the $72 billion in taxpayer money which included solar panel subsidies or the afterthought of wind power or the other get-rich-quick schemes in alternative energy we have tried since 2009 – it even happened without nuclear power, the best and most viable zero-emissions energy of them all.  It also happened without banning existing energy. The big change instead came because America switched to natural gas, and that was thanks to science and the free market. Due to that switch, energy emissions haven’t looked this good in 20 years.  Coal emissions haven’t looked this good in 30 years.

Believe it or not, to environmental fundraisers, that is a really bad thing.

With CO2 emissions dropping, activists have started to wind up the machine against methane and they note it is worse than CO2 – without mentioning that it is short-lived or that it is the primary component in cleaner natural gas. Instead, ‘natural’ is being removed from the term completely and replaced with ‘shale’.

The answer to climate change according to many environmentalists is to just throw money at it:

Environmentalists…who know nothing at all about how real innovation works think they can just throw money at one thing and penalize another and capitalism magic happens. The real world, outside of academia and fundraising brochures, is a lot messier. Like evolution, innovation has starts and stops, sometimes it tries a few times and fails. What has never worked is assuming that if we spend 100X as much money, the process will go 100X as fast.

Environmentalists should be happy. Unfortunately, many are too busy worried about their pet agendas.

Shrinking Waves May Save Sea Ice

2014-06-10 sn-seaice

The whole global warming issue is pretty controversial, and one of the reasons for that is that–no matter what the consensus on the science might be–there’s actually a long and convoluted path from “human carbon emissions make the world warmer” to answering the question “what should we do about it?”

One of the big uncertainties, of course, is the cost-benefit analysis of policies designed to slow global warming. That’s what the Freakonomics guys did in one of their chapters from Super Freakonomics, and their conclusion was that–assuming climate change is real–there might not be any policy to stop it that is worth the cost. That claim, as you can imagine, landed them in some hot water.

But there are other uncertainties as well. So the planet gets warmer. So ice at the poles melts and sea levels rise, right? Well, maybe not so fast:

It’s a nagging thorn in the side of climatologists: Even though the world is warming, the average area of the sea ice around Antarctica is increasing. Climate models haven’t explained this seeming contradiction to anyone’s satisfaction—and climate change deniers tout that failure early and often. But a new paper suggests a possible explanation: Variability in the heights of ocean waves pounding into the sea ice may help control its advance and retreat.

That’s Carolyn Gramling writing for Science. She goes on to summarize the paper’s theory: warmer climate means lower waves, lower waves means less pounding on sea ice, less pounding on sea ice means slower melting to the point where (as noted above) sea ice in Antarctica is actually growing instead of shrinking.

The reality is that the Earth’s atmosphere and land and ecosystems and the sun’s radiation all work together to form a very, very, very complex system full of all kinds of negative and positive feedback loops that we know nothing about. This is just one example. Ice has been growing since at least 1979 despite projections, but no one had a clue. Now they have one but it is, of course, still just a clue. As science goes: this is great. When the data doesn’t line up with your predictions, it means you’re not understanding something and you have a chance for a new discovery.

But as a basis for expensive, global policy-making goes, this is not so great. The one thing all policies to thwart global warming have in common is making energy more expensive which will have the effect of lowering growth which will have the effect of keeping more people in the developed world in poverty for longer. We can be much more certain about that then we can about the corresponding threat from global warming. After all, we can’t even predict if the sea levels will rise at all, let alone by how much, so how can we begin to make a careful evaluation of the cost/benefit of policies to mitigate this unknown danger?

The consensus on global warming is often trotted out as a cudgel with which to beat skeptics, but this isn’t really effective once you step back and realize that climate change, itself, is only one part of a much, much more complex puzzle.