From a Briefing Paper of the Global Warming Policy Foundation
About this briefing
In December 2014 the Royal Society published A Short Guide to Climate Science, a layman’s introduction to the key issues in the subject. The guide was accompanied by a video and was widely reported in the media.
The authors who wrote the guide were not identified. Nor were the members of the Royal Society asked whether they endorsed it or not. So in referring to it herein as the ‘Royal Society’ guide we only mean to indicate who published it. We have no way of knowing how many Royal Society Fellows actually agree with it.
Many commentators were concerned that the guide was profoundly misleading, misrepresenting major points while overlooking some of the key issues and question marks over the science, glossing over them as if they were of little consequence. As an example, when the Royal Society addresses the long-term rise in Antarctic sea ice it says that ‘changes in winds and in the ocean seem to be dominating the patterns of sea ice change in the Southern Ocean around Antarctica’. In reality, what is being described in these words is a recently proposed hypothesis, so while a reader of the Short Guide might come away with the impression that science had a broad under-standing of what was happening in the Southern Ocean, what they should have been told was that the changes in Antarctic sea ice are not understood. In a time of universal overconfidence, to be willing to state what is not known is an essential, albeit controversial, duty of scientists.
This report attempts to give a more accurate picture of climate science and to add in the caveats and to explain the gaps in our knowledge over which the Royal Society guide drew a veil.
The Royal Society, quite properly, does not draw policy conclusions from the meager science they present (and misrepresent), but they, most assuredly, know that others will.
This report was prepared by, and endorsed by, the undersigned authors, all of whom are members of the Academic Advisory Council of the GWPF. It does not represent a corporate position of the GWPF itself.
Professor Robert Carter
Professor Ross McKitrick
Professor Vincent Courtillot
Professor Ian Plimer
Professor Freeman Dyson
Dr Matt Ridley
Professor Christopher Essex
Sir Alan Rudge
Dr Indur Goklany
Professor Nir Shaviv
Professor Will Happer
Professor Fritz Vahrenholt
Professor Richard Lindzen
The Small Print
1 Is the climate warming?
Yes. Earth’s average surface air temperature has increased by about 0.8◦C (1.4◦F) since 1900, with much of this increase taking place since the mid-1970s. A wide range of other observations such as sea-level rise, reduced Arctic sea ice extent and increased ocean heat content provide incontrovertible evidence of a warming Earth.
A fuller picture:
This is hardly an important question. The Earth’s surface is always warming or cooling, or on some occasions barely changing. What is important is that the change referred to is small and imperfectly measured. It should also be stressed that the Royal Society guide does not mention the role of the time window they are using for comparison. The climate has cooled since the mid-Holocene climatic optimum 8,000 years ago, and the warming of the past few decades is relatively small in comparison.
Surface temperatures have increased on average by about 0.8◦C since1900. There was a rise of around 0.5◦C at the start of the twentieth century, followed by a small fall from 1940 to 1970. From then until the late 1990s temperatures rose by around 0.5◦C. Differences of a tenth of a degree are insignificant. The temperature is virtually unchanged from that at the beginning of the century. The two periods of increase are indistinguishable, although the earlier increase cannot be attributed to increased carbon dioxide.
The relation of other observations such as sea-level rise, Arctic sea ice extent and ocean heat content all depend on more factors than global mean temperature, and are hardly incontrovertible evidence of warming. That said, the possible acceleration of ocean heat content accumulation and sea level rise are close to the limits of our ability to detect and the values involved cannot be reconciled to each other. Depending on the timescale, other observational datasets are still more equivocal: global sea ice levels declined for several decades but are now above their long-term mean.
2 How do scientists know that recent climate change is largely caused by human activities?
Human activity leads to emissions of greenhouse gases (causing warming), and of other pollutants that produce small particles in the atmosphere (which can have both cooling and warming effects). The dominant influence of human activities on recent climate change is clear from an understanding of the basic physics of the greenhouse effect and from comparing the detailed patterns of recent climate change with those expected from different human and natural influences. Only when human influences on the composition of the atmosphere are incorporated can models reproduce observed changes in climate.
A fuller picture:
The warming effect of greenhouse gases is widely recognized. However, the direct effect is known to be relatively small: about 1◦C for a doubling of carbon dioxide levels. Most of the warming predicted in climate models arises from knock-on effects (‘feedbacks’) associated with changes to cloud cover, atmospheric humidity and so forth. Feedback processes are mostly hypothetical and are therefore much more uncertain, and some may even have cooling effects.
The Royal Society guide claims that models fail to explain recent warming unless they incorporate anthropogenic forcing. This assertion depends on the readily falsifiable claim that models correctly replicate natural variability. Models fail on natural variability, therefore the Royal Society’s claim fails in the real world. However, even if the conclusion were correct, it would still be consistent with the view that the climate is not very sensitive to greenhouse gases since the observed changes have been small (to the point of being indiscernible for the past 15 years).
3 Carbon dioxide is already in the atmosphere naturally, so why are emissions from human activity significant?
Human activities have significantly disturbed the natural carbon cycle by extracting long-buried fossil fuels and burning them for energy, thus releasing CO2 to the atmosphere. The concentration of CO2 has increased by 40% since the Industrial Revolution.
A fuller picture:
Carbon dioxide levels have been increasing steadily. A body of evidence points to this being due to human effects – emissions from burning of fossil fuels and land-use changes – although the Earth’s carbon dioxide budget is not sufficiently understood to accurately quantify the human and natural contributions.
Natural fluxes in the carbon cycle are an order of magnitude higher than manmade emissions, so any natural imbalances, perhaps as a result of temperature changes, can swamp human contributions. Regardless, given the aforementioned evidence that the sensitivity to carbon dioxide is low, anthropogenic GHGs cannot by