How big and soon and where will temp changes be?

[venturerite]

How possible is it that the changes in temp will continue to increase until, for a vague example: by the year 2020 we'll have 160 degree summers and -100 degree winters? (or some variation of extreme perpetual temp alteration)?

Nearly everyday reached 100 degrees in Salt Lake City all summer, will next summer be 105 all summer? And will the crops in Cali fail further than before to an even greater cold this coming winter?

Dan

 

[Ivan Seeking]

I don't think anyone expects changes that large. To the extent that we do see radical changes, it will certainly not be that soon according to any model that I've seen [i.e. predictions from various models]. Realistically, floods, pests, population displacement, more intense storms, and disease are the biggest concerns. Heat waves are a concern as well, but not 160 degree heat waves.

On the down side, mass extinctions only require something like a 10 degree increase in the average temp, so we don't need 160 degree days to be in trouble. Currently, I believe that we have seen something like a 2 degree increase in the average temp over the last century, but I would have to review the literature to be sure about the latest conclusions and any consensus that might exist. And of course, only part of the temp rise is attributed to human activity with any confidence.

 

[Skyhunter]

Ivan Seeking,

The increase in global temperatures the last century is ~.7^oC. And all of that warming can be attributed to human activity, since man made aerosols are artificially suppressing the increased radiative forcings from GHG.

As Pinker et al demonstrate, as the atmosphere clears, instantaneous radiative flux continues to increase while solar irradiation has remained constant or even decreased.

 

[Ivan Seeking]

Eleven of the last twelve years (1995–2006) rank among the 12 warmest years in the instrumental record of global surface temperature9 (since 1850). The updated 100-year linear trend (1906 to 2005) of 0.74°C [0.56°C to 0.92°C] is therefore larger than the corresponding trend for 1901 to 2000 given in the TAR of 0.6°C [0.4°C to 0.8°C].

So according to this, the change has been between 1 and 1.7 degrees F over the last century, with a mean of .74 degrees C as you stated.

Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.12 This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations”. Discernible human influences now extend to other aspects of climate, including ocean warming, continental-average temperatures, temperature extremes and wind patterns (see Figure SPM.4 and Table SPM.2). {9.4, 9.5}

...It is very unlikely that climate changes of at least the seven centuries prior to 1950 were due to variability generated within the climate system alone. A significant fraction of the reconstructed Northern Hemisphere inter-decadal temperature variability over those centuries is very likely attributable to volcanic eruptions and changes in solar irradiance, and it is likely that anthropogenic forcing contributed to the early 20th-century warming evident in these records. {2.7, 2.8, 6.6, 9.3}...

http://ipcc-wg1.ucar.edu/wg1/Report/AR4WG1_Pub_SPM-v2.pdf

venturerite, if you go to page 13 of 18 of this report, you will find some predictions about future climate change.