The world of pop-climatology falls into two camps: global-warming deniers and global-warming alarmists, Or as they call themselves: skeptics and realists. To most liberals, it sounds like the usual din of conservatives too scientifically illiterate to grasp the basic facts of a major issue. Given that many conservatives struggle to comprehend a theory as simple as Evolution, one cant be too shocked at their hamhandedness with climate change.
Few liberals have dared to take a closer look at the present state of climatology, or, particularly, at the theory of anthropogenic global warming (AGW). There is strong evidence that the planet STOPPED warming in 1998 – that while there was considerable warming during the 20th century, during the 21st century there has been none at all. This lack of recent warming is referred to among climatologists as the “hiatus” – and the issues are (1) whether it’s real, and if so (2) what that means for AGW theory generally.
An introduction (or refresher) to basic climate science is in order. The earth’s climate – and in particular, its mean surface temperature – is variable, and always has been. Earth can be thought of as having a “heat budget” – however much heat arrives from the sun should in equal measure be radiated back into space. An imbalance will lead to either warming or cooling. Factors that cause the imbalance are referred to as “forcings.” Many have been identified. The most common, and most powerful, is solar variability. The well-known “Little Ice Age” roughly corresponded with a period of reduced solar output. When climatologists look at the global warming that occurred during the 20th century, they are unable to find any forcing – other than the actions of mankind.
The earth’s atmosphere, as a function of the planet’s size, is quite small. If the earth were shrunk down to the size of a basketball, the atmosphere (defined as 90% of all the air) would only rise about 1mm above the surface. Pictured otherwise, the distance from sea level down to the center of the earth’s core is about 4000 miles (New York to Berlin). But the distance from sea level up to the 90% point of the atmosphere is only about 10 miles (Central Park to Prospect Park). And so it’s no surprise that a human population of seven billion can easily change atmospheric chemistry.
From various measures, we know that CO2 concentration before the Industrial Revolution was about 280 parts per million (PPM). When the Mauna Loa Observatory began measuring CO2 concentration in 1958, that value had already risen to about 315PPM. Today it is close to 400PPM.
CO2, as greenhouse gases go, is sort of a weenie. Water vapor does a whole lot more warming, simply because there’s a whole lot more of it up there. Methane is 70X more powerful, pound for pound. Doubling the earth’s atmospheric CO2 concentration would NOT, by itself, warm the planet very much. The way a little CO2 can produce lots of warming is through feedback. You add CO2, the earth warms a little bit, more water vapor goes into the atmosphere, glaciers retreat (making the earth less reflective), and soon a little warming becomes a lot of warming.
To call that an oversimplification would be a disservice to legitimate oversimplifications the world over. The defining characteristic of climate models is their complexity – indeed climate is itself a complex system. The work of climatologists is often the building of complicated models that can correctly “replay” the earth’s climate over time. Put otherwise, climate scientists take time-series data, and then create algorithms to reproduce that data post hoc.
Climate isnt the only complex system we’re all familiar with. Economies are also complex systems – and macroeconomists struggle just as much to predict future states of the economy. We expect the business cycle of recession and recovery to continue, but we’re not good at predicting when they will come, or how strong they will be. After the fact, economists excel in post hoc explanations as to why or how this or that bubble led to all manner of boom or bust – but macroeconomic models are inept at making all but the crudest of predictions. Analogously, meteorologists understand the seasons and can predict the weather several days in advance. But should you book that beach place for Labor Day Weekend? You wont know till late August….
The fault lies not with climatology or macroeconomics, but with climate and economy. Complex systems are fundamentally NOT given to predictive modeling. In the case of Global Warming, so much is at stake, that climatologists do the best they can. But as Yogi said, it’s tough making predictions – especially about the future….
Which brings us to the hiatus – which no climate model predicted. Post hoc explanations are just now arriving. The 3 most prominent are Trenberth, Cowtan and Kosaka. Trenberth’s work shows that while the atmosphere wasnt warming over the past 15 years, the deep oceans (depths of 700-2000m) were. Cowtan, a mathematician, shows that climatologists did a piss-poor job of sampling surface temperatures – that the hiatus is illusory; global warming has only accelerated these past 15 years. Finally, Kosaka accepts the hiatus – he has a shiny new model that reproduces the time-series of surface temperatures over the past 40 years. The model is dead, long live the model.
Seeing the obvious contradictions among those 3 papers, you might wonder about the “consensus” among climate scientists we always hear so much about. On climate change and the theory of AGW, there is indeed broad agreement among climatologists that (1) mankind has increased the amount of CO2 in the atmosphere; and that (2) increases in atmospheric CO2 will warm the planet. But there is NO consensus on HOW MUCH warming will ensue as a consequence. The range of predictions across different climate models for a doubling of CO2 (from 280 to 560PPM, eg) goes from 1C degree on up to about 7C degrees. At the low end, global warming is a manageable nuisance. At the high end, it’s the end of life as we know it.
Among climatologists, perhaps the most prominent critic of AGW theory is Richard Lindzen of MIT. He is eminently respectable and well regarded – he just happens to differ in his opinion on the “HOW MUCH” question, and is more generally skeptical of the ability of climatologists to predict future states of the earth’s climate. He fairly notes that no climatological model predicted the present hiatus – so what good are any of them? Lindzen’s own models, FYI, come in at the bottom of the range.
From a public policy standpoint, our perception of and reaction to AGW are critical to some of the planet’s most vulnerable populations. There’s good scholarship that warming adversely affects GDP in the developing world, and also causes political unrest. On the other hand, curbing emissions in the developing world will almost certainly slow down economic growth, which has raised tens of millions out of poverty in recent decades, and stands to raise hundreds of millions more in the near future. India has the most to gain – and lose – given that they have a large, growing, energy-intensive economy, and a geography that makes them especially vulnerable to rising seas and intensified storms.
And a question should be fairly asked: whether our best tactic to address climate change is to invest in today’s economy, and make use of cheap energy, in the hope that future generations, with higher incomes and better technology, will have better solutions to the environmental problems brought on by industrialization.
I’m not a climatologist, and I lack the training to parse out their various papers and models. But I do know a bit about complexity and complex systems – and I therefore do not find climatology’s failure to predict the present hiatus to be all that troubling. Pauses in warming occurred at other times during the 20th century – 15 years is not enough time to declare that the larger warming trend has ended, or that climatological predictions of future warming are to be dismissed. But while there is consensus that warming will continue – as CO2 concentrations inexorably rise through this century – the science is simply NOT settled as to how much will occur.
The curb-emissions-or-die position of environmentalists is, fundamentally, Malthusian – in the sense that it posits the finiteness of a particular resource, and the inability of human ingenuity to manage it. Malthusian arguments are NOT however always wrong – Easter Island is the most popular example. And at this point, with present incomes and technology, it is fair to observe that humanity simply lacks the means to cope with a 3C+ degree increase in mean surface temps.
In the face of this uncertainty – and with the welfare of hundreds of millions of poor people hanging in the balance – I’d offer these policy prescriptions. Western economies, like the US, wd do well to heavily subsidize investment in renewables, and to return to nuclear power. (More Americans have died from windpower than from nuclear!) Even if global warming comes in at the low range of predictions, the US is not served by paying monopoly prices for oil to its adversaries in the Middle East and Russia; and America doesnt need to sicken its populations downwind from coal-fired electric plants.
The developing world, however, should stay the course. Higher energy costs are effectively a death sentence for the millions it will trap in poverty. India, it is interesting to note, is taking a middle course – which may be sensible given its special circumstances.
Going forward we will have a better idea of just how much (or how little) warming will happen – one hopes that as the time comes, the economies and technologies that we grow today will give us the means to manage the issues of tomorrow.