SUNDAY TELEGRAPH 8/4/07
A dangerous climate
By Bob Carter
The latest IPCC report, published on Friday, is the most alarming yet: not for its claims of human-caused global warming, writes the leading environmental scientist Bob Carter, but for its lack of scientific rigour
At 4C, it is cold in the storage refrigerator. One needs to rug up well to work here. I am at the US headquarters of the Ocean Drilling Programme at Texas A&M University, studying seabed cores from the southwest Pacific Ocean.
As the cores pass through the logging sensor that measures their character, the rhythmic pattern of ancient climate change is displayed before me. Friendly, fossiliferous brown sands for the warm interglacial periods, and hostile, sterile grey clays for the cold glaciations.
For more than 90 per cent of recent geological time, the cores show that the earth has been colder than today. We modern humans are lucky to live towards the end of the most recent of the intermittent, and welcome, warm interludes.
know not what. Climate, it seems, changes ceaselessly in either direction: sometimes cooling, sometimes warming, often for reasons that we do not yet fully understand.
Cores through polar ice reveal, contrary to received wisdom, that past temperature changes were followed - not preceded, but followed - by changes in the atmospheric content of carbon dioxide. Yet the public now believes strongly that increasing human carbon dioxide emissions will cause runaway warming; it is surely a strange cause of climate change that naturally postdates its supposed effect?
Am I the first scientist to have observed these climate patterns? Of course not. That climate changes frequently, rapidly and sometimes unpredictably has been conventional knowledge among earth environmental scientists since the early days of ocean drilling in the 1970s.
Yet we do not read about natural climate change in the everyday news. Instead, newspapers, radio and television stations bludgeon us with a merciless stream of human-caused global-warming alarmism, egged on by a self-interested gaggle of journalists, environmental lobbyists, scientific and business groups, church leaders and politicians, all of whom preach that we must "stop climate change" by reducing human CO2 emissions.
The body from which most of these groups get their information is the Inter-governmental Panel on Climate Change (IPCC). It is also the organisation that advises national governments. The IPCC has issued three substantial statements, the First (1990), Second (1995) and Third (2001) Assessment Reports, each of which incorporates the research and opinions of many hundreds of qualified scientists.
Its 20-chapter, 1,572-page Fourth Assessment Report was released on Friday. The full reports are detailed and compendious, and each is therefore accompanied by a short chapter termed a Summary for Policymakers (SPM) that is designed for political application.
Many distinguished scientists refuse to participate in the IPCC process, and others have resigned from it, because in the end the advice that the panel provides to governments is political and not scientific. Although at least -$50 billion has been spent on climate research, the science arguments for a dangerous human influence on global warming have, if anything, become weaker since the establishment of the IPCC in 1988.
Yet the rhetoric of IPCC alarm has been successively ramped up, from "the observed [20th-century temperature] increase could be largely due to... natural variability" (1990); to "the balance of the evidence suggests a discernible human influence on climate" (1995): to "there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities" (2001); to it is "90 per cent probable" that the recent warming is "due to the observed increase in anthropogenic greenhouse gas concentrations" (2007). What can the evidence be for these increasingly dramatic warnings?
The IPCC advances three main categories of argument for a dangerous human influence on climate. The first is that, over the 20th century, global average temperature increased by about 0.7C, which it did, if you accept that the surface thermometer record used by the IPCC is accurate.
More reliably, historical records and many geological data sets show that warming has indeed occurred since the intense cold periods of the "little Ice Ages" in the 14th, 17th and 19th centuries. The part of this temperature recovery which occurred in the 20th century is the "global warming", alleged by climate alarmists to have been caused by the accumulation of human-sourced CO2 in the atmosphere.
However, our most accurate depiction of atmospheric temperature over the past 25 years comes from satellite measurements (see graph below) rather than from the ground thermometer record. Once the effects of non-greenhouse warming (the El Niño phenomenon in the Pacific, for instance) and cooling (volcanic eruptions) events are discounted, these measurements indicate an absence of significant global warming since 1979 - that is, over the very period that human carbon dioxide emissions have been increasing rapidly.
The satellite data signal not only the absence of substantial human-induced warming, by recording similar temperatures in 1980 and 2006, but also provide an empirical test of the greenhouse hypothesis as understood by the public - a test that the hypothesis fails.
The second category of alarmist argument rests upon circumstantial evidence. It is epitomised by the former American vice-president Al Gore's film An Inconvenient Truth, which claims that human greenhouse emissions are causing accelerated melting of icecaps, dangerous increases in the rate of sea-level rise, increases in the frequency and intensity of droughts or catastrophic storms, and enhanced rates of biodiversity loss.
Every such circumstantial argument ignores two basic facts. The first is that all environmental phenomena fluctuate in their rate, frequency or intensity as part of the normal workings of our dynamic planet. The second, which follows, is that whether a particular short-term change over, say, the early 21st century has any human causation can only be assessed when all the causes of natural environmental change are fully understood.
Many different fields of study are involved and all are the subject of intensive ongoing research. From this research emerges one inescapable fact: that in no case yet has any climate-sensitive environmental parameter been shown to be changing at a rate that exceeds its historic natural rate of change, let alone in a way that can be unequivocally associated with human causation.
This generally happy news, does not mean that the planet has rendered a judgment of "not guilty" upon us, but that while the jury remains out a presumption of innocence applies. The scientific equiv-alent of this is Occam's Razor (the principle of simplicity), under which environmental change is assumed to be natural until cause can be demonstrated otherwise.
The third line of the IPCC argument, and the least convincing of all, is the use of computer calculations to assess the likely future course of the climate. Many billions of dollars have been expended by major climate research groups around the world on honing complex General Circulation Models (GCMs) of the ocean and atmosphere. Each of these models comprises more than a million lines of code and all are deterministic, which is to say that they specify the climate system from the first principles of physics.
However, GCMs are not predictive tools, which is why even their proponents refer to their output as climate "scenarios" and not "predictions". For many parts of the climate system, such as the behaviour of turbulent fluids or the processes that occur within clouds, our knowledge of the physics is incomplete, which requires the extensive use of "parameterisation" (for which read "educated guesses") in the computer models.
Hendrik Tennekes, a former director of research at the Royal Dutch Meteor-ological Institute who pioneered methods of multi-modal forecasting, remarked recently: "A [GCM] prediction 50 or 100 years into the future is an idle gesture." That the IPCC relies so heavily upon complex GCM-generated scenarios as the basis for its climate alarmism is alarming in its own right; it also reflects the absence of any strong empirical evidence for human-caused climate change, as outlined earlier.
So the evidence for dangerous global warming forced by human carbon dioxide emissions is extremely weak. That the satellite temperature record shows no substantial warming since 1978, and that even the ground-based thermometer statistic records no warming since 1998, indicates that a key line of circumstantial evidence for human-caused change (the parallel rise in the late 20th century of both atmospheric carbon dioxide and surface temperature) is now negated.
In February this year, the IPCC released the SPM for its Fourth (Science) Assessment Report, followed on Friday by the full report. Using GCMs, the new report projects a temperature increase by 2100 of between 1.1 to 6.4C. This is a wider range than the 1.6 to 5.8C projected in the third assessment report, which implies less rather than more certainty regarding future temperature trends. The report also continues the regrettable IPCC practice of allocating arbitrary numerical probability estimates to the causes and risks of future climate change.
In the present state of knowledge, no scientist can justify the statement: "Most of the observed increase in globally averaged temperature since the mid-20th century is very likely due [90 per cent probable] to the observed increase in anthropogenic greenhouse gas concentrations," as stated in the 2007 SPM.
The environmental catchphrase of the moment is "sustainability". It is therefore a good question to ask how much longer politicians, responding to pressure from the IPCC and other lobby groups, can sustain the fiction that dangerous human-caused climate change is upon us.
That climate change is part of our planet's normal, dynamic behaviour is not in doubt. Nor should there be any doubt about the need for governments to prepare sensible response plans for future climate change, both warmings and coolings. But reflection on recent climatic episodes like the "little Ice Ages" makes it plain that future climatic coolings will cause much greater damage to our societies than will mild warmings similar to that of the 20th century.
That 20th-century warming, the most recent of many previous warm phases of similar or greater magnitude, was dangerous or human-caused, or even that the warming has continued after 1998, both yet remain to be demonstrated.
Bob Carter is a research professor at James Cook University, Australia and former chair of the Earth Sciences Panel of the Australian Research Council and former Director of the Australian Office of the Ocean Drilling Programme. His webpage is http://members.iinet.net.au/~glrmc/new-page-1.htm