The public debate on climate change, continuing while the Climate Action and Low Carbon Development Bill 2015 makes its passage through the Oireachtas, entered a new phase during the past week with the holding of the Maynooth conference, “Meeting the Challenge of Climate Justice: From Evidence to Action”.
As it concluded one speaker made the notable statement that “the Irish equivalent of keeping fossil fuels in the ground is to reduce agricultural emissions”, which seemed to capture the mood of the conference.
The statement, implying that Irish agricultural emissions should be reduced by about two-thirds, represents such a serious challenge to the vital interests of this country that it must not pass uncontested.
As a scientist I fully support the consensus position that greenhouse gases have a warming influence on the climate system and that international action to limit build-up is required. But I do not agree that we are facing a planetary emergency requiring the abandoning of vital national interests when climate legislation is being considered.
The observed warming of the global climate system since the late 19th century amounts to about 0.85°C. It took place during two separate periods, 1910-45 and 1970-98, with a 25-year period of cooling intervening. The warming in the period 1910-1945, when greenhouse gas emissions were small, was as great as in the period 1970-1998, when emissions were much greater.
Cautious
That complexity is captured by the cautious statement of the Intergovernmental Panel on Climate Change (IPCC) 2013 report: “ It is extremely likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations”.
A breakdown of the global temperature graph into its land and sea components provides further grounds for caution. That shows that in the period 1910-1945 land and sea temperatures increased at the same rate, while in the later period 1970-1998 land temperatures increased at almost twice the rate of the sea surfaces.
Why this major difference? At a discussion at an international scientific conference in which I took part recently it became clear that the reason is unknown. That uncertainty and the fact that the global sea surface temperature has increased by only a third of a degree since the 1940s suggests a degree of caution is needed from those proclaiming we face a planetary emergency.
Most of the reason for concern about greenhouse gas increase arises from the projections of climate models, some of which suggest a further warming of up to 4°C by the end of the century if emissions continue unabated. Most models, however, have considerably overestimated the rate of surface warming over the past 15 years, and, crucially, none has been able to simulate the virtual absence of warming at tropical mid-tropospheric levels (around the mass centre of the atmosphere) indicated by satellite observations over this period.
Many other reasons exist for caution over climate model projections. Foremost is the increased uncertainty in estimates of climate sensitivity (the warming that would result from a carbon dioxide doubling) given by the IPCC in going from its 2007 to its 2013 report, and the recent emergence of credible estimates that lie below the current IPCC range. Moreover, there is the increased uncertainty in the recent IPCC report in the attribution of the factors contributing to sea level rise.
As an Irish citizen, the first thing to be taken into account is that Ireland is a major food exporting country, with over 90 per cent of our principal agricultural outputs – dairy products and beef – sold abroad. Consequently, Ireland’s agricultural emissions as a share of our total emissions – at 32 per cent – are more than three times the EU average. Per unit of output, our emissions in the dairy sector are the lowest in the EU, and in the beef sector among the lowest. It is our government’s national duty to do its utmost to maintain Ireland’s position as a low-emissions food producer and exporter – a vital matter of national interest, but also in the interests of EU and world food security.
We should play our part as an EU state in reaching an agreement on global emissions cuts at the UN’s Paris December climate meeting. However, we should approach the negotiations in a rational manner, based on the latest scientific findings and on pragmatism, not ideology.
Ray Bates is adjunct professor of meteorology at UCD, former professor of meteorology at the Niels Bohr Institute, University of Copenhagen, and a senior scientist at NASA. He has served as an expert reviewer of IPCC reports.