Last week the Intergovernmental panel on climate change (IPCC) issued their latest high profile report on the current understanding of climate change.
Their main conclusion is that there can be little doubt that man is responsible for at least half of the rise in global temperatures since the 1950s, due to man-made greenhouse gases.
As a geophysicist myself, I cannot argue with the science behind the greenhouse effect, which is based on sound physical principles.
To that end, the science behind how greenhouse gases such as carbon dioxide would cause warming of the atmosphere, in my mind, is settled.
But there are areas of the science which cannot be described as anywhere near settled, where there are uncertainties that cannot be easily dismissed.
These uncertainties have been an area that I have focused on over the last few years on this climate blog.
The one area which is perhaps as crucial as any is that of climate model performance, because governments around the world are using climate projections to make long term planning decisions, in particular on future energy generation.
Judge for yourself if this part of the science is settled, from the IPCC report, Section D1:
‘The observed reduction in surface warming over period 1998-2012 is due roughly in equal measure to a reduced trend in radiative forcing and cooling from internal variability, which includes a possible redistribution of heat within the ocean (medium confidence).’
‘There is low confidence in quantifying the role of changes in radiative forcing in causing the reduced warming trend.'
‘There may also be a contribution from forcing inadequacies and, in some models, an overestimate of the response to increase greenhouse gas and other anthropogenic forcing.’
To highlight this area of uncertainty further, in late 2009, I wrote an article which you can read HERE in which I look at the then apparent slowdown in global warming.
In it, I discuss research from the Met Office Hadley Centre.
In the research the authors discuss why they believe a levelling off of temperatures can be expected at times.
The research shows that near zero temperature trends for intervals of a decade or less can be expected due to the model’s internal climate variability.
But crucially, the research rules out zero (temperature) trends for intervals of 15 years or more.
We are now 15 years into the so called ‘pause’ in global temperatures and the research further illustrates that this crucial part of climate science is far from settled, and it’s disappointing that more time wasn’t given to this issue across the media in the days since the report was published.
That said the authors of this report are in little doubt that over the longer term, man is altering our climate by adding greenhouse gases to the atmosphere.
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