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Recent research in the journal Nature Geosciences, mainly by scientists based in Britain, on the possibility of limiting global warming to a 1.5C rise above pre-industrial levels has been seized on by climate change sceptics.

They claim that the models predicting global warming used by the Intergovernmental Panel on Climate Change (IPCC), a United Nations research body, have been exaggerating the problem. The Daily Mail reported that "according to these models, temperatures across the world should now be at least 1.3 degrees above the mid-19th century average… But the British report demonstrates that the rise is only between 0.9 and 1 degree". If true this would be a significant reduction of observed warming of about 30%. The Mail followed this up with a letter from the Labour MP Graham Stringer saying that action on global warming was now no longer urgent.

Climate change academics such as the economist Nicholas Stern also welcomed the report since it raised the possibility of achieving a 1.5C target, something that previously had looked out of reach to them. Until recently, a target of limiting temperature rises to 2C was widely accepted as sufficient to prevent potentially catastrophic climate change. The growing evidence of extreme weather events being linked to the present degree of global warming of 1C caused a rethink, and the IPCC is currently writing a report on the issue.

After the controversy surrounding the Nature Geosciences publication, the Carbon Brief website carried out a detailed analysis of the data, with input from the authors themselves. This showed that the Mail had misrepresented the conclusions. The work, which was never intended to assess the accuracy of climate models, compared current data on warming (from 2015) with a climate model prediction in 2020. This was done to address the specific needs of the research but is not comparing like with like because temperatures are predicted to rise between the two dates. If a correction is made then the disparity between model predictions and actual temperatures falls by about half to 0.17C for 2015.

Another factor is that the predictions of models depend on their input data. There are several data sets that are available for global temperatures which give significantly different results. The one from the Met Office, chosen by the British researchers, was used because it went back as far as 1860, but the accuracy of readings from this period are known to be more doubtful than those from slightly later. Also, the Met Office database excludes readings from large areas of the Arctic. If the Nasa data set is applied, taking measurements from 1880 onwards, then there was 0.06C more warming in 2015 than predicted by the models. Similar results are found with some other data sets.

Blips in the models have occurred, where they have over-predicted actual temperatures, but these were due to the effect of the volcanoes El Chichon in 1982 and Pinatuba in 1991. The ash from such eruptions can significantly depress global temperatures but random events like these cannot be factored into any model.

Analysis by Carbon Brief, using five data sets for global temperatures available for the period 1880-2016, found generally close agreement with the IPCC models. The Berkeley Earth data shows warming has been 11% faster than the model average, and the Met Office figures give 6% slower warming. The remainder lie in between. Taking readings since 1970, it is true that the models predict slightly higher temperatures than those observed, but only by 0.01C or 0.02C. There was a slowdown in the growth of air temperatures from 1999 to 2014 due to natural cyclical effects. That caused a speedup of ocean circulation in the Pacific and had the effect of dragging more heat down into the deep ocean and away from the atmosphere. This has now ended.

So, overall, there is no reason to believe that global warming has been ‘exaggerated by faulty models’. Also, leaving the models aside, there is no doubt at all that 2014, 2015 and 2016 were the hottest years ever recorded, with surface air temperatures now more than 1C above pre-industrial levels for the first time. The evidence is rapidly growing linking extreme weather events, such as droughts, floods and heatwaves, to this still relatively small increase in temperature.

Urgent action to avoid catastrophic climate change

This means that the need for urgent action to avoid catastrophic climate change effects remains, including addressing the need to limit warming to 1.5C. One of the authors of the Nature Geosciences paper, professor Piers Foster, says that "our paper confirms the need for much increased urgent action from around the world if society stands a chance of limiting warming to 1.5C".

Another co-author, professor Michael Grubb – along with prominent climate change academics like Nicholas Stern – thinks there is now a chance of achieving the 1.5C target if immediate action is taken. He had previously ruled out such as target as being "incompatible with democracy", since it would require the elimination of carbon emissions in seven years. Grubb pointed out that the annual decrease in carbon output required to have a chance of reaching this target had only happened three times in modern history: during the great depression, the second world war, and the collapse of the Soviet Union. His pessimism was understandable given the abysmal track record of the major capitalist states over the past 30 years on tackling global warming.

The more optimistic view of achieving 1.5C is based on the new possibility he has raised of having 20 years to hit the target. This breathing space follows from the findings of his paper, as well as the unexpected current plateau in emissions from the largest polluter China, and the dramatic fall in the price of solar and wind power. If we assume we now have 20 years, which would be a very welcome reprieve, there is still very little prospect that decisive action will be taken by the big polluting powers. This is because the present mechanism, the Paris accord brokered by the UN in December 2015, was toothless even before Donald Trump pulled the USA out.

Unfortunately, there must also be very great doubt over the basis of professor Grubb’s new more optimistic prediction. Firstly, his caveat that immediate action must be taken is extremely unlikely to be realised. Secondly, the analysis by Carbon Brief indicates that there will probably be very little if any undershoot of actual temperatures compared to model predictions. Also, the present levelling-off of China’s emissions is not guaranteed to continue, as it is largely dependent on government policy, such as the decision to cut back on cement production. When the bureaucracy comes under pressure, there could be a reversal of present trends (see Green China to Save the World?, Socialism Today No.201, September 2016).

The fall in the price of renewables has boosted the deployment of solar cells and wind turbines, but the impact this is having is still too small and too slow to make a major difference (Trump Dumps Paris Accord, Socialism Today No.210, July 2017). The most likely prospect is that the time left to take action to have a possibility of limiting warming to 1.5C will be much less than 20 years. And there is no chance of this happening with the present business-as-usual approach of the big powers. Only a rapid move to replace predatory capitalism with a democratic socialist planned economy would create the conditions where we can begin to tackle the threat the global warming.

Committee for a workers' International publications

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