Cool heads required

At a recent global warming conference in Exeter called by UK prime minister Tony Blair, all the usual fears were aired. Yet real debate about climate change seems to be strictly prohibited.

The week before, another conference organised by the Scientific Alliance at London’s Royal Institution raised critical questions about the global warming thesis. This time the Royal Society’s president Sir Bob May received frontpage coverage for arguing that the event would be biased and dangerous.

‘On one hand we have the IPCC [Intergovernmental Panel on Climate Change], the rest of the world’s major scientific organisations, and the government’s chief scientific adviser, all pointing to the need to cut emissions’, he wrote. ‘On the other we have a small band of sceptics, including lobbyists funded by the US oil industry, a sci-fi writer, and the Daily Mail, who deny the scientists are right. It is reminiscent of the tobacco lobby’s attempts to persuade us that smoking does not cause lung cancer. There is no danger this lobby will influence the scientists. But they don’t need to. It is the influence on the media that is so poisonous.’ (1)

But in fact, those labelled ‘sceptics’ and those regarded as ‘mainstream’ actually share much in common. Professor Richard Lindzen of Massachusetts Institute of Technology (MIT), usually regarded as a sceptic but also a lead author for the IPCC, agrees that there is consensus among scientists. That consensus is as follows:

1. While there are inconsistencies in the temperature data, it is very likely that the world has got a bit warmer over the past 100 years – 0.6 degrees Celsius, on average, give or take 0.2 degrees either way.

2. That carbon dioxide is a greenhouse gas. The more carbon dioxide in the atmosphere, the warmer the world will tend to get.

3. That human activity has led to a significant increase in carbon dioxide levels, from 280 parts per million in the centuries before 1750, to 380 parts per million now.

4. Economic trends will tend to further increase carbon dioxide levels – so it is very plausible that the world will get warmer in the coming decades, all other things being equal.

The big questions in this debate are about the causes, extent and significance of climate change. While carbon dioxide is one potential cause, it is far from alone. The climate has always been in a state of flux, over shorter or longer periods, so it is likely that there are many natural factors at work in addition to any effect humans might be having.

As to the extent of climate change, almost everyone agrees that we simply don’t know. It is true that carbon dioxide levels will increase, but a law of diminishing effect applies – so, as more carbon dioxide is pumped into the atmosphere, each extra percentage increase has less and less effect (2).

If carbon dioxide levels did eventually double from their pre-industrial levels, all other things being equal, it is likely that the temperature would rise by about 1.2 degrees Celsius. That represents a noticeable warming – but nothing that would demand urgent global action.

But once there is a general temperature increase, what would be the effect on the rest of the climate system? This is where the arguments start. If the temperature goes up, so does the level of evaporation from the oceans, which adds all sorts of complications. If there is more water vapour in the atmosphere, it could create a positive feedback effect: the more the atmosphere holds, the warmer the world is likely to get; the warmer it gets, the more water vapour is produced.

If the water vapour clumps together as clouds, these clouds could reflect radiation back out into space, which would tend to reduce the temperature – or they could act as a ‘blanket’, retaining heat. The net effect of clouds is still unknown.

Then there is also the effect of ‘aerosols’, tiny particles which tend to reflect sunlight back out into space. It is thought they may also have a role in how clouds turn to rain – but how exactly is not really understood.

Many more factors are involved in climate. Scientists just don’t seem to know enough about the physics of many of these processes, or how these different processes interact.

Scientists’ best option at present seems to be to simplify these processes and interactions, making many educated guesses along the way, and try to model them using supercomputers. These models are the basis of most of the climate change reports we read about. However, given that many important elements will be oversimplified or unknown in these models, drawing firm conclusions from them is difficult.

We don’t even have sufficiently good data to be able to gauge the accuracy of these models. Satellites to measure temperature evenly across the Earth’s surface have been operational since 1979. Data prior to 1979 relies on surface weather stations and weather balloons, which are not evenly spread around the world. Good records exist for North America and Europe over a period of about 100 years, but there have never been many stations for the 70 per cent of the Earth covered by water, or the 38 per cent of the rest that is desert or mountains.

This means that scientists cannot say for sure what the average temperature of the Earth was in 1900 – and the problem gets worse the further back we go. If the starting point data for a model is wrong, even slightly wrong, it could have a major impact on the outcome. Worse, it is impossible to test the model. If you want to see how good a model is, perhaps the best way to test it is to start it from as long ago as possible, and see if the results match what really happened. This doesn’t work if we don’t know what really happened more than two or three decades back.

As Tim Ball, Kenneth Green and Steven Scroeder, three North American climate researchers, note: ‘Surface temperature records for the world are inadequate to determine the average annual temperature of the earth. The uncertainty in the global “normal” surface temperature – estimated to be 13.9 degrees Celsius…a decrease from an earlier estimate of 15 degrees Celsius… is almost twice as large as the estimated global warming in the last 100 years.’ (3)

Perhaps these models provide us with insights into what we don’t know, but they can’t predict the future of our climate – at least, not yet. When we have more powerful computers, greater understanding of the physical processes involved and a longer history of good data, it’s likely that models will provide better predictions.

A final source of uncertainty is that nobody knows how societies will change over the next century. Models rely on a range of ‘scenarios’ about future economic growth, population, emissions, and so on. While a wide range of different scenarios are employed, it’s a safe bet that no single scenario will actually be accurate.

For example, the most alarming figures for temperature change – up to 5.8 degrees Celsius – are based on high economic growth, massive increases in emissions, and a high level of positive feedbacks. These are really ‘worst-case’ scenarios – the IPCC concluded that temperature increases outside the range 1.5 to 4.5 degrees Celsius were ‘unlikely’. Yet these worst-case scenarios dominate the public discussion of climate change.

The one thing we can be pretty sure about is that, one way or another, the climate will change. Even during the course of the twentieth century, we have seen global temperatures rise in the period up to 1940, decline through to the 1970s (creating fears of a new Ice Age), and rise again thereafter. Only the last stage of this process could plausibly be caused by greenhouse gas emissions, which suggests there are substantial natural variations going on regardless of anything humans do.

The problem is that the scientific debate has been politicised, which distorts the presentation and discussion of the evidence. Environmentalists are particularly to blame here, for they have a moral message to convey: that human beings are screwing up the world. This message has now been taken on board across society, and has almost become common sense. In an atmosphere where every new report is either leapt upon to produce further gloomy conclusions about our future, or prematurely dismiss the case for global warming, it’s unlikely that the science remains uncorrupted.

For example, in January 2005, one of the authors of the IPCC’s work on hurricane activity and climate change, Chris Landsea, resigned from the forthcoming fourth IPCC assessment report. He was angered by a news conference in which the lead author of the report’s Observations section, Dr Kevin Trenberth, appeared to state that the recent spate of hurricanes was partly caused by global warming.

‘It is beyond me why my colleagues would utilise the media to push an unsupported agenda that recent hurricane activity has been due to global warming’, wrote Dr Landsea in an open letter explaining his resignation. ‘Given Dr Trenberth’s role as the IPCC’s Lead Author responsible for preparing the text on hurricanes, his public statements so far outside of current scientific understanding led me to concern that it would be very difficult for the IPCC process to proceed objectively with regards to the assessment on hurricane activity.’ (4)

A group of researchers who appear to be broadly sympathetic to the global warming thesis, including Professor Hans von Storch of Hamburg University, have also raised concerns about the conduct of the discussion. ‘The concern for the “good” and “just” case of avoiding further dangerous human interference with the climate system has created a peculiar self-censorship among many climate scientists. Judgments of solid scientific findings are often not made with respect to their immanent quality but on the basis of their alleged or real potential as a weapon by “sceptics” in a struggle for dominance in public and policy discourse.’ (5)

They note that this leads to a research outlook that heavily promotes mitigation (ie, reducing the human effect on climate) over adaptation (ie, changing society to allow it to cope with a different climate). This is a problem, because if climate continues to change, as it surely will, perhaps what we need most is development that makes society as climate-proof as possible. But that discussion has barely begun, while the obsession with cutting carbon dioxide emissions has dominated.

It is likely that we will only be able to understand and cope with climate change through a rigorously critical examination of data, models and theories. But the climate created by this politicised debate may make that impossible.

Read on:

spiked-issue: Global warming

(1) Under-informed, over here, Guardian, 27 January 2005

(2) Carbon dioxide absorbs a specific, narrow band of the electromagnetic spectrum. As carbon dioxide is added to the atmosphere, more of this narrow band is absorbed – leaving less of this narrow band to be absorbed by further increases in carbon dioxide concentration. The upshot is that the amount of additional warming from each additional unit of carbon dioxide falls.

(3) The Science Isn’t Settled, Public Policy Sources, June 2004

(4) Chris Landsea Leaves IPCC, 17 January 2005 (posted on the University of Colorado Prometheus service)

(5) Sustainability and the issue of climate change, by Hans von Storch, Nico Stehr and Sheldon Ungar, November 2004 [pdf format]