Arthur Dahl 4 February 2014
Climate sceptics have recently been claiming that global warming has paused since 1998 despite rising levels of greenhouse gases, confirming their belief that it is not man-made and therefore that no action is necessary. This is the latest argument in an on-going campaign of disinformation on the issue, complicated by the ideological and political dimensions that the debate has taken in some countries (USA, Canada, Australia). A recent study has shown that almost a billion dollars a year has been spent on anti-climate-change propaganda over the last decade, often demonstrating that disinformation repeated often enough is accepted as fact. In systems of government by lobby, science does not carry much weight. This has produced many sceptics who are not convinced by the scientific evidence, often because it is not their specialty and/or because of the seeds of doubt intentionally planted in the media and the public debate with great skill and effect. Some ask if one should give equal time for the arguments for and against, but this implies that both are searching for the truth, when in fact one side is defending an ideological position and economic interests.
This issue was addressed in the creation of the Intergovernmental Panel on Climate Change (IPCC), which is charged with weighing all the scientific evidence and defining the present expert consensus. It is a transparent process involving a thousand climate experts and all the governments in the UN, and it is very conservative in what it accepts as scientifically valid. Its conclusions are supported by the national Academies of Science and international scientific unions. The 42 climate models, 2 million gigabytes of data, and 9,200 peer-reviewed publications on which the 5th Assessment Report is based are a very solid foundation for its conclusions. In its latest report, its most optimistic scenario is for a CO2 concentration in the atmosphere of 475ppm, when in fact the science suggests that climate change can only be avoided by bringing it back to 350ppm from the present 400ppm. This shows how conservative it is. When there is such a mechanism to define the science, we should accept that as such and leave the details to the experts.
In fact, there is not a "pause" in global warming since 1998, only a reduction in the rate of increase, and only in the atmosphere and upper ocean. Other parts of the system, particularly the deeper ocean below 700 m with an enormous heat capacity, continue to warm rapidly. Part of the problem is the choice (by climate sceptics) of 1998 as the starting point for their comparison, as that was the year of the great El Nino Southern Oscillation when the atmosphere was much warmer than usual; when you start measuring from a peak in natural variability, obviously the subsequent years seem to lag behind. There is good evidence that increased heat storage in the oceans may have reduced the heat available to warm the atmosphere, and other natural variations account for more of the difference. Aerosols are another contributor to cooling, and have been rising with the massive increase in coal burning in China and elsewhere since 1998. The release of greenhouse gases has continued to accelerated during this period, so there is every reason to expect a rapid rebound to the long-term curve in atmospheric warming in the years ahead.
The IPCC explains this change in the rate of increase as follows: "The observed reduction in surface warming trend over the period 1998 to 2012 as compared to the period 1951 to 2012, is due in roughly equal measure to a reduced trend in radiative forcing and a cooling contribution from natural internal variability, which includes a possible redistribution of heat within the ocean (medium confidence). The reduced trend in radiative forcing is primarily due to volcanic eruptions and the timing of the downward phase of the 11-year solar cycle. However, there is low confidence in quantifying the role of changes in radiative forcing in causing the reduced warming trend. There is medium confidence that natural internal decadal variability causes to a substantial degree the difference between observations and the simulations; the latter are not expected to reproduce the timing of natural internal variability. There may also be a contribution from forcing inadequacies and, in some models, an overestimate of the response to increasing greenhouse gas and other anthropogenic forcing (dominated by the effects of aerosols)." (IPCC AR5 WGI Summary for Policymakers, p. 13.)
The World Bank could not be considered ideologically liberal, yet it has come out strongly in favor of action on climate change (see http://climatechange.worldbank.org/sites/default/files/Turn_Down_the_heat_Why_a_4_degree_centrigrade_warmer_world_must_be_avoided.pdf). The remaining capacity of the atmosphere to absorb carbon without going over 2°C in warming is 565 gigatons of CO2, while proven reserves of conventional fossil fuels contain 2,795 gigatons of carbon, not counting shale gas or tar sands. The experts closest to the issue say that, to avoid accelerating climate change, we must achieve a carbon-free economy by 2050, and leave 80% of the existing fossil fuel reserves in the ground, and this transition is technically possible. Obviously writing proven reserves off their asset accounts is anathema to the fossil fuel industry, petroleum-exporting countries and traditional economic circles, which is why they are willing to spend so much to deny it. While climates have always changed over millennia, they have never been subject to the rapid rate of human transformation of the atmosphere that we are experiencing today (except perhaps after asteroid strikes). This is an enormous ethical challenge, and would seem to reflect Baha'u'llah's warning about civilization carried to excess.