Expert view: Has global warming stopped?
Last updated on 11 January 2013, 5:35 pm
Earlier this week data published by the UK’s national meteorological office in December 2012, predicting global temperature changes to 2017, was interpreted as implying that global warming had stopped.
The Met Office dismissed media reports that its data suggests this is the case. Instead it said the earth will warm a little less in the next ten years than previously predicted but long term warming continues.
Confusion arose after an update to its decadal climate model reduced its estimate for the period 2012-2016 from 0.54 to 0.43°C.
This was picked up by BBC Radio and the UK Daily Telegraph who reported that warming was at a ‘standstill’.
The Met Office says this is incorrect – but what do experts think?
The Science Media Centre approached four climate scientists for their professional opinions.
Dr Richard Allan, Reader in Climate Science at the University of Reading, said:
“Global warming is not ‘at a standstill’ but does seem to have slowed down since 2000 in comparison to the rapid warming of the world since the 1970s.
“In fact, consistent with rising greenhouse gases, heat is continuing to build up beneath the ocean surface.
“This indicates that changes in ocean circulation are in part responsible for the recent slower rate of surface warming. The way the ocean distributes the extra energy trapped by rising greenhouse gases is critical in determining the new Met Office forecasts of global surface temperature over the coming decade and is an area of active research.
“These decadal forecasts are very much experimental – they are at the cutting edge of the science and are technically very challenging. The Met Office are being open and transparent by making the forecasts available to allow a proper validation to occur. The Met Office is one of about 10 groups performing these type of forecasts worldwide and all predict a warming over the coming decade.
“Nothing in their data leads me to think that global warming due to human influence has stopped, or is irrelevant. It hasn’t, and it isn’t.”
Prof Myles Allen, Head of the Climate Dynamics Group at the University Of Oxford, said:
“Comparing the expected temperature for 2013-2017 with a single exceptionally warm year (1998), as some reports have done, is just daft. 1998 was around 0.2 degrees warmer than the 1996-2000 average, largely thanks to a massive, once-a-century El Nino event.
The IPCC predicted a warming of 0.1-0.2 degrees per decade due to human influence back in 2000. That means the one-off impact of that El Nino event was equivalent to about 20 years of the expected background warming trend So, unsurprisingly, 20 years later, expected temperatures have risen so that an average year is now as warm as that exceptionally hot year.
“That said, a lot of people (not the IPCC) were claiming, in the run-up to the Copenhagen 2009 conference, that ‘warming was accelerating and it is all worse than we thought’. What has happened since then has demonstrated that it is foolish to extrapolate short-term climate trends. We did see unexpectedly fast warming from the mid-1990s to the early-2000s, but the IPCC, quite correctly, did not suggest this was evidence for acceleration.
“While every new year brings in welcome new data to help us rule out the more extreme (good and bad) scenarios for the future, it would be equally silly to interpret what has happened since the early-2000s as evidence that the warming has stopped.”
Prof Sir Brian Hoskins, Director, Grantham Institute for Climate Change at Imperial College London, said:
“The current news item that the Met Office now predicts no global warming in the period up to 2017 is based on the latest 5-year forecast run with their new climate model. Such forecasts are at the frontiers of the subject and form part of a research programme in this area in the Met Office and elsewhere, but should not be considered to be predictions.
“One interpretation of the forecasts is for little warming from 1998 until 2017. This is consistent with a multi-decadal fluctuation in temperature that presently opposes the continued upward trend. However the two supported one another during the rapid warming in the 1990s and can be expected to do this again in the future, leading to another period of rapid warming.
“The forecast results also suggest that half the years in the period to 2017 would be expected to give new record global temperatures.”
Prof Chris Rapley, Professor of Climate Science at University College London, said:
“I despair of the way data such as this is translated as ‘global warming has stopped’! Global mean temperatures – whether measured or predicted – are not the issue. What matters is the energy balance of the planet and the changes that an energy imbalance will drive in the climate system – as well as the consequences for humans.
“90% of the energy imbalance enters the ocean and is not visible to the global mean surface temperature value. The continuing rise in sea level demonstrates ongoing energy accumulation in the ocean (as well as a contribution from melting land ice).
“Even if the global mean temperature were to remain unchanged, if the geographic patterns of temperature and rainfall change, the consequences will still be potentially severe. We only need to look at what is going on in Australia at this very moment.”