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Climate model forecast is revised | Climate model forecast is revised |
(1 day later) | |
By David Shukman Science editor, BBC News | By David Shukman Science editor, BBC News |
The UK Met Office has revised one of its forecasts for how much the world may warm in the next few years. | The UK Met Office has revised one of its forecasts for how much the world may warm in the next few years. |
It says the average temperature is likely to be 0.43 C above the long-term average by 2017, as opposed to an earlier forecast suggesting a difference of 0.54C. | |
The explanation is that a new kind of computer model using different parameters has been used. | The explanation is that a new kind of computer model using different parameters has been used. |
The Met Office stresses that the work is experimental. | |
It says it still stands by its longer-term projections that forecast significant warming over the course of this century. | |
The forecasts are all based on a comparison with the average global temperature over the period 1971-2000. | The forecasts are all based on a comparison with the average global temperature over the period 1971-2000. |
The earlier model had projected that the period 2012-16 would be 0.54C above that long-term average - within a range of uncertainty from 0.36-0.72C. | The earlier model had projected that the period 2012-16 would be 0.54C above that long-term average - within a range of uncertainty from 0.36-0.72C. |
By contrast the new model, known as HadGEM3, gives a rise about one-fifth lower than that of 0.43C - within a range of 0.28-0.59. | By contrast the new model, known as HadGEM3, gives a rise about one-fifth lower than that of 0.43C - within a range of 0.28-0.59. |
This would be only slightly higher that the record year of 1998 - in which the Pacific Ocean's El Nino effect was thought to have added more warming. | This would be only slightly higher that the record year of 1998 - in which the Pacific Ocean's El Nino effect was thought to have added more warming. |
If the forecast is accurate, the result would be that the global average temperature would have remained relatively static for about two decades. | If the forecast is accurate, the result would be that the global average temperature would have remained relatively static for about two decades. |
Blog suspicions | Blog suspicions |
An apparent standstill in global temperatures is used by critics of efforts to tackle climate change as evidence that the threat has been exaggerated. | An apparent standstill in global temperatures is used by critics of efforts to tackle climate change as evidence that the threat has been exaggerated. |
Climate scientists at the Met Office and other centres are involved in intense research to try to understand what is happening over the most recent period. | Climate scientists at the Met Office and other centres are involved in intense research to try to understand what is happening over the most recent period. |
The most obvious explanation is natural variability - the cycles of changes in solar activity and the movements and temperatures of the oceans. | The most obvious explanation is natural variability - the cycles of changes in solar activity and the movements and temperatures of the oceans. |
A Met Office spokesman said "this definitely doesn't mean any cooling - there's still a long-term trend of warming compared to the 50s, 60s or 70s. | A Met Office spokesman said "this definitely doesn't mean any cooling - there's still a long-term trend of warming compared to the 50s, 60s or 70s. |
"Our forecast is still for temperatures that will be close to the record levels of the past few years. | "Our forecast is still for temperatures that will be close to the record levels of the past few years. |
"And because the natural variability is based on cycles, those factors are bound to change the other way at some point." | "And because the natural variability is based on cycles, those factors are bound to change the other way at some point." |
The fact that the revised projection was posted on the Met Office website without any notice on December 24 last year has fuelled suspicions among bloggers. | The fact that the revised projection was posted on the Met Office website without any notice on December 24 last year has fuelled suspicions among bloggers. |
However the Met Office says the data had been published in a spirit of transparency as soon as it became available from the computer that produced it. | However the Met Office says the data had been published in a spirit of transparency as soon as it became available from the computer that produced it. |
Future forcings | Future forcings |
It describes the decadal projections as part of an experimental effort launched in 2004 to fill the gap between daily weather forecasts and century-long estimates for climate change. | It describes the decadal projections as part of an experimental effort launched in 2004 to fill the gap between daily weather forecasts and century-long estimates for climate change. |
But this is an emerging and highly complex area of science because of the interplay of natural factors and manmade greenhouse gases at a time when a key set of temperatures - in the deep ocean - is still relatively unknown. | But this is an emerging and highly complex area of science because of the interplay of natural factors and manmade greenhouse gases at a time when a key set of temperatures - in the deep ocean - is still relatively unknown. |
One aim of attempting to project the climate on this timescale is to be able to rapidly check the accuracy of the models being used. | One aim of attempting to project the climate on this timescale is to be able to rapidly check the accuracy of the models being used. |
A paper published last month in the journal Climate Dynamics, authored by scientists from the Met Office and 12 other international research centres, combined different models to produce a forecast for the next decade. | A paper published last month in the journal Climate Dynamics, authored by scientists from the Met Office and 12 other international research centres, combined different models to produce a forecast for the next decade. |
It said: "Decadal climate prediction is immature, and uncertainties in future forcings, model responses to forcings, or initialisation shocks could easily cause large errors in forecasts." | It said: "Decadal climate prediction is immature, and uncertainties in future forcings, model responses to forcings, or initialisation shocks could easily cause large errors in forecasts." |
However the paper concluded that, "in the absence of volcanic eruptions, global temperature is predicted to continue to rise, with each year from 2013 onwards having a 50 % chance of exceeding the current observed record". | However the paper concluded that, "in the absence of volcanic eruptions, global temperature is predicted to continue to rise, with each year from 2013 onwards having a 50 % chance of exceeding the current observed record". |
Scrutiny of Met Office forecasts and climate science generally is set to increase in the build-up to the publication of the next assessment by the UN's Intergovernmental Panel on Climate Change (IPCC) in September. | Scrutiny of Met Office forecasts and climate science generally is set to increase in the build-up to the publication of the next assessment by the UN's Intergovernmental Panel on Climate Change (IPCC) in September. |