Today's generation could see a world 2oC warmer than the pre-industrial era
Release Date 24 October 2011
If greenhouse gas emissions continue to increase, global temperatures are projected to cross a threshold of 2oC above the pre-industrial era between 2040 and 2060- well within the lifetime of many people currently alive. Even if crossing the 2oC threshold becomes unavoidable, reducing emissions could delay this from happening by up to several decades, buying valuable time for the world to adapt to climate change.
These are the conclusions of new work by scientists from the National Centre for Atmospheric Science (NCAS) based at the University of Reading's Walker Institute, from the UK Met Office and from the University of Oxford, just published in Nature Climate Change.
Dr Manoj Joshi, lead author of the work, says that considering the question of ‘when are serious impacts expected?', as opposed to ‘what serious impacts are expected?' adds an extra dimension to the debate about reducing emissions of greenhouse gases.
He said "It is not just about avoiding potentially dangerous climate change, but also about buying time for adaptation."
In the recent Copenhagen and Cancun Accords on climate change it was agreed that if global warming exceeded 2oC above pre-industrial levels, the consequences for food, water and biodiversity would become increasingly serious. Examples of potential impacts would be a significantly increased likelihood of heat waves and droughts, or marked reductions in crop yields.
Rapid reductions in global greenhouse gas emissions over the next few decades will be needed to avoid the 2oC threshold. However, even such rapid reductions are likely to lead to levels of warming that require some adaptation. Information about when particular thresholds are likely to be crossed is useful in deciding when adaptation measures, which typically have a long lead time, should begin.
Large parts of Eurasia, North Africa and Canada are projected to experience temperatures that exceed the 2oC threshold by 2040 - earlier than the rest of the world. In addition, thresholds will be exceeded in individual years before being exceeded consistently year on year, because of natural variability in climate. Such variability has profound implications for planners who must decide if a single year or two above a potentially dangerous threshold can be borne, and at which point adaptation measures should be introduced.
Dr Joshi said: "This approach to communicating the impacts and uncertainties of climate change draws attention to rates of change rather than just the change itself. It complements existing methods, and should be employed more widely."
Facts and figures:
1. In the highest emissions scenario considered (none of which involve specific policies to reduce greenhouse gas emissions), global CO2 emissions continue to rise throughout the 21st century, reaching almost 30 gigatonnes of carbon per year by 2100. In the lowest emissions scenario, carbon emissions rise until the 2040s and then fall below 10 gigatonnes per year by 2100.
2. Over the 20th century, global temperatures have risen to around three quarters of a degree above pre-industrial levels. Using the Hadley Centre dataset, the warmest year in the record (1998) was around 0.9oC above pre-industrial levels, due to a combination of global warming and El Nino.
ENDS
For more information please contact Rona Cheeseman, University of Reading Press Office, on 0118 378 7388, email r.cheeseman@reading.ac.uk
Or Kathy Maskell, Walker Institute communications, on 0118 378 7380, email k.maskell@reading.ac.uk
Notes to editors:
- 1) Journalists should seek to credit Nature Climate Change as the source of stories covered.
- 2) Reference: Projections of when temperature change will exceed 2°C above pre-industrial levels (2011) Manoj Joshi, Ed Hawkins, Rowan Sutton, Jason Lowe and David Frame, Nature Climate Change.
- 3) The National Centre for Atmospheric Science (NCAS) is a world leader in atmospheric science. Research areas include climate, weather, atmospheric composition, modelling and atmospheric observations. www.ncas.ac.uk. NCAS climate scientists at Reading are part of the University of Reading's Walker Institute for Climate System Research which aims to improve understanding and prediction of our changing climate and its impacts over seasons, decades and beyond, across a range of applications. www.walker-institute.ac.uk