Excerpts from the IPCC AR5 SYR released today in Copenhagen – with a focus on more recent cryospheric issues, and with a bias towards higher confidence statements.
“Over the period 1992 to 2011, the Greenland and Antarctic ice sheets have been losing mass (high confidence), likely at a larger rate over 2002 to 2011. Glaciers have continued to shrink almost worldwide (high confidence). Northern Hemisphere spring snow cover has continued to decrease in extent (high confidence). There is high confidence that permafrost temperatures have increased in most regions since the early 1980s in response to increased surface temperature and changing snow cover. {1.1.3}
The annual mean Arctic sea-ice extent decreased over the period 1979 to 2012, with a rate that was very likely in the range 3.5 to 4.1% per decade. Arctic sea-ice extent has decreased in every season and in every successive decade since 1979, with the most rapid decrease in decadal mean extent in summer (high confidence).
Anthropogenic influences have likely affected the global water cycle since 1960 and contributed to the retreat of glaciers since the 1960s and to the increased surface melting of the Greenland ice sheet since 1993. Anthropogenic influences have very likely contributed to Arctic sea-ice loss since 1979 and have very likely made a substantial contribution to increases in global upper ocean heat content (0–700 m) and to global mean sea-level rise observed since the 1970s. {1.3.1; Figure 1.10}
The global mean surface temperature change for the period 2016-2035 relative to 1986-2005 is similar for the four RCPs and will likely be in the range 0.3°C-0.7°C (medium confidence). This assumes that there will be no major volcanic eruptions or changes in some natural sources (e.g., CH4 and N2O), or unexpected changes in total solar irradiance.
Year-round reductions in Arctic sea ice are projected for all RCP scenarios. A nearly ice-free Arctic Ocean (When sea-ice extent is less than one million km2 for at least five consecutive years. ) in the summer sea-ice minimum in September before mid-century is likely for RCP8.512 (medium confidence). {2.2.3, Figure 2.1}
It is virtually certain that near-surface permafrost extent at high northern latitudes will be reduced as global mean surface temperature increases, with the area of permafrost near the surface (upper 3.5 m) projected to decrease by 37% (RCP2.6) to 81% (RCP8.5)for the multi-model average (medium confidence). {2.2.3}
The risks associated with temperatures at or above 4°C include substantial species extinction, global and regional food insecurity, consequential constraints on common human activities, and limited potential for adaptation in some cases (high confidence).
It is virtually certain that global mean sea-level rise will continue for many centuries beyond 2100, with the amount of rise dependent on future emissions. The threshold for the loss of the Greenland ice sheet over a millennium or more, and an associated sea-level rise of up to 7 m, is greater than about 1°C (low confidence) but less than about 4°C (medium confidence) of global warming with respect to pre-industrial temperatures.
For mitigation scenarios that stabilize concentrations (without overshoot) in the range of 430-530 ppm CO2-eq by 2100, annual investments in low carbon electricity supply and energy efficiency in key sectors (transport, industry and buildings) are projected in the scenarios to rise by several hundred billion dollars per year before 2030.”
