IPCC 5th Assessment Report

The Intergovernmental Panel on Climate Change 5th Assessment report was released this week. I have read the summary for policymakers, and it doesn’t make for comforting reading. Here are some of the main issues that stood out for me. These are simplified results, for the full content, read the report.

The digested read, digested.

Its going to get hotter and dryer where its already hot and dry, and wetter where it is already wet. The ice is going to melt more quickly and raise the sea levels. The air and ocean temperatures will rise and expand, rising sea levels even further. Coastal areas will experience more flooding and tidal surges. The climate will change in unpredictable ways, but it will change. Even if we stopped burning fossil fuels today some of this will happen anyway, if we don’t stop soon then our great grand-children will inherit a very different world to the one we grew up in.

Our buildings will need to resist overheating, protect from flooding, deal with increasing precipitation, provide more shade, and cause fewer greenhouse gases to be emitted in their production, construction, operation and demolition.

The Main Issues (for me)

-‘Warming of the climate system is unequivocal, and since the 1950’s many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished,sea level has risen and the concentrations of greenhouse gases have increased’

-‘The globally averaged combined land and ocean surface temperature…show a warming of 0.85 deg C over the period 1880-2012’

-‘The rate of warming since 1951 is 0.12 deg C per decade.’

-‘The average rate of ice loss from glaciers around the world, separate from ice sheets, was very likely 226 gigatonnes per year 1971-2009 and 275 gigatonnes per year over the period 1993-2009.’ In other words the rate of ice loss from glaciers is accelerating.

-‘The average rate of ice loss from the Greenland ice sheet has very likely substantially increased from 34 gigatonnes per year over the period 1992-2001 to 215 gigatonnes per year over the period 2002-2011.’ This is an increase of over 6 times within the period.

-‘The average rate of ice loss from the antartic ice sheet has likely increased from 30 to 147 gigatonnes per year over the period 2002-2011.’

-‘There is high confidence that permafrost temperatures have increased in most regions since the early 1980s. Observed warming was up to 3 deg c in parts of Northern Alaska(early 19880s to mid 200s) and up to 2 deg c in parts of the Russian European North(1971-2010).’

-‘The rate of sea level rise since the mid 19th Century has been larger than the mean rate during the previous two millenia (high confidence). Over the period 1901-2010, global mean sea level rose by 0.19m.’

-‘It is very likely that the mean rate of global averaged sea level rise was 1.7mm/year between 1901-2010, 2.0mm/year between 1971 and 2010 and 3.2mm/year between 1993 and 2010.’ In other words the rate of rise is rising.

‘The atmospheric concentrations of CO2, methane and nitrous oxides have increased to levels unprecedented in at least the last 800,000 years.’

-The atmospheric concentrations of the greenhouse gases CO2, CH4 and N2O have all increased since 1750 due to human activity. In 2011 the concentrations of these greenhouse gases …exceeded the pre-industrial levels by about 40%, 150% and 20% respectively.

-‘Annual CO2 emissions from fossil fuel combustion and cement production were 8.3 gigatonnes of CO2/year averaged over 2002-2011(high confidence) and were 9.5 gigatonnes/year in 2011, 54% over the 1990 level.’ It is interesting that cement production gets mentioned in the same sentence as fossil fuel production. Yet we never hear of any policy measures aimed at reducing cement production or use, why is that?

‘Continued emission of greenhouse gases will cause further warming and changes in all components of the climate system. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.’

Global surface temperature change for the end of the 21st century is likely to exceed 1.5 deg C relative to the period 1850-1900…’ for most future scenarios. It is likely to exceed 2 deg C for some scenarios.

‘It is virtually certain that there will be more frequent hot and fewer cold temperature extremes over land areas on daily and seasonal time-scales as global mean temperatures increase. It is very likely that heat waves will occur with a higher frequency and duration. Occasional cold winter extremes will continue to occur.’

‘It is very likely that the Atlantic Meriodonal Overturning Circulation (AMOC) will weaken over the 21st Century. Best estimates and range are… 11%…- 34%… It is likely that there will be some decline in it by about 2050.’ The AMOC is a long name for the Gulf Stream. Any likelihood of it weakening or changing ought to worry us very much.

‘Changes in the global water cycle in response to the warming over the 21st Century will not be uniform. the contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions.’ So mostly dry and hot regions will get mostly dryer and hotter and mostly wet regions will get wetter, mostly.


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