Climate change and trace gases

James Hansen, Makiko Sato, Pushker Kharecha, Gary Russell, Dav

id W Lea and Mark Siddall

Sea-level change yields an estimate of ice sheet area change.

Vostok temperature change divided by 2

5 kyr timing gap between forcing and response

Milankovitch (1941) theory of the ice ages

Spring & GHG

We expect the rate of sea-level rise to be maximum when NH spring insolation peaks.

diverge gradually increasing slower falling below most scenarios, but only slightly.

A substantial part of the CO2 is taken up by the ocean quickly. But the CO2 added to the ocean, in effect, exerts a back pressure on the atmosphere that prevents all of the addedCO2 from being absorbed by the ocean until someCO2 is buried in ocean sediments, which requires a very long time.

1/4 60% 90%

sustained cut of fossil fuel BC emissions of 50%

20, 100 and 500 years

(C) 0.04, 0.17 and 0.67

(d) 0.15, 0.18 and 0.24

the Arctic warming due to these pollutants exceeds the Arctic warming due to CO2.

Figure 10a shows growth of the climate whipsaw during the Plio-Pleistocene.

Changing tilt of the Earth’s spin axis, with its predominant 41 kyr frequency, principally determines annual insolation variation versus latitude (figure 10b). The 41 kyr variations are increasingly large, in absolute and relative insolation, towards the pole.

precession (thus the season when the Earth is closest to the Sun) becomes more important, with its predominant 23 kyr frequency.

Thus, ca 100 kyr eccentricity variations come into play along with precession. Figure 10c shows insolation forcing at the latitude of the Laurentide ice sheet (60 N), exhibiting both the 23 and 100 kyr frequencies.