Is our climate today changing? Yes, it is of course, but then again it always has. Studying the past enables us to see present changes in a longer-term perspective and to understand how the climate system works. However, it is vitally important to understand that just because climate has changed in the past, does not mean that we can therefore attribute recent changes to natural causes alone. A number of different modelling studies (see the illustration below) have shown very neatly that it is not possible to explain the past 100 years of global temperature change without including both natural (solar and volcanic) and human (greenhouse gas emissions) influences.
Greenhouse gases (such as carbon dioxide, methane and nitrous oxide) warm the Earth’s atmosphere by absorbing and re-radiating heat that would otherwise be lost to space. You can think of greenhouse gases a bit like an atmospheric duvet. The more greenhouse gases, the thicker the duvet, the more heat is retained, warming the planet. The physics of the greenhouse effect, as this process is known, have been understood for well over 100 years.
In our opinion, the scientific foundation for and multitude of evidence of global climate change are conclusive. The IPCC, an international collaboration of 110 of the world’s governments, recently released its most recent summary of global climate science (late September 2013). The Working Group I report references over 9000 studies (about two thirds of which were new since the previous report in 2007) and incorporates over 54,000 review comments from over 1000 expert reviewers. A pretty thorough job, then.
In the report, it is stated that warming of the climate system is unequivocal and that it is extremely likely (IPCC terminology referring to a likelihood of 95 – 100%) that human influence has been the dominant cause of recent observed warming. Atmospheric carbon dioxide levels are at their highest level for at least 800,000 years and continued emissions will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained emissions reductions.
We’re not attempting here to provide an in-depth analysis of the state of climate science on one page of a website to do with peatlands! Suffice to say that, despite the multitude of opinions, viewpoints and attitudes that are inevitably displayed whenever climate change is discussed, our opinion on the matter rests with the vast body of objectively collected empirical and modelling evidence.
So apart from their role as an archive for records of the past, how else do peatlands fit into the climate change picture? Globally, peatlands store significant amounts of carbon; they cover only a few percent of the Earth’s surface but store up to a third of all terrestrial carbon, just over 600 gigatonnes. The UK’s peatlands store around 3000 million tonnes of carbon, twenty times more than the whole of the UK’s forests. Since this, and a range of other important environmental functions, have been recognised, peatlands have been increasingly protected and even managed and restored to maximise their carbon storage potential. However, it is also known that a multitude of factors, including climate change but also drainage for agriculture, peat cutting or afforestation, can turn peatlands from a carbon sink to a potential source of CO2 and methane. The IUCN Peatland Programme estimates that ten million tonnes of CO2 are lost to the atmosphere every year from the UK’s damaged peatlands alone. Understanding and managing global peatland carbon dynamics under current and future climate change scenarios is therefore vitally important.
IPCC 5th Assessment Report, Summary for Policymakers, downloadable here.
Yu, Z., Loisel, J., Brosseau, D. P., Beilman, D. W. and Hunt, S. J. 2010. Global peatland dynamics since the Last Glacial Maximum. Geophysical Research Letters 37, doi:10.1029/2010GL043584.
IUCN Peatland Programme briefing note on Peatlands and Climate Change, downloadable here.