2007a). We will refer to these experiments as the 6Kyr runs. Coastlines, vegetation, and ice sheets are identical to the PI simulations. CO2 and aerosols are also identical to the PI while there is a modest reduction in methane concentration (from 760 to 650 ppbv). Orbital parameters representative of 6000 years before the present are taken from Berger and Loutre (1991). Most significantly, orbital precession causes the seasonal cycle of insolation in the Northern Hemisphere to amplify, while the duration of summer is reduced; the seasonal amplitude of ?SWv,TOA? increases by 2.5% relative to the PI climate. Enhanced obliquity causes more high-latitude insolation in the annual mean. We note that the sum of all mid-Holocene forcing agents is symmetric about the equator in the annual average. Six different model simulations of 6Kyr are analyzed.
b. Show
2, LGM, and 6Kyr experiments in sections 3b(1)–3b(3). The change in annual mean PPenny in the three forcing experiments is plotted against the change in annual mean AHTEQ and ?SST in the top and bottom panels of Fig. 10, respectively. In the LGM and 2XCO2 experiments the intermodel spread in both the change in PPenny and AHTEQ is larger than the ensemble average change and so the sign of the change is ambiguous (cf. the solid red and blue squares with the spread in the red and blue crosses across both axes); the ensemble average change in PCent and AHTEQ is not significantly different from zero in the LGM and 2XCO2 runs. This result is surprising, especially in the LGM case, where one would expect that the large Laurentide ice sheet in the 
Northern Hemisphere would lead to a deficit of absorbed shortwave radiation (a positive change ?SWInternet,TOA?) leading to a cooling in the Northern Hemisphere (relative to the Southern Hemisphere), a decrease in ?SST, a southward shift in PCent, and more northward AHTEQ. This result suggests that intermodel differences in the spatial structure of climate feedbacks can play a bigger role in setting the interhemispheric contrast of the temperature and energetic response than does the interhemispheric contrast in climate forcing and boundary conditions themselves.
I establish the outcome round the all the three pushing experiments right here, immediately after which subsequent familiarize yourself with the newest 2XCO
(top) Change in annual mean precipitation centroid vs change in cross-equatorial heat transport in the atmosphere in the 2XCO2 simulations (each red cross is a different ensemble member), 6000 years before present simulations (green crosses), and Last Glacial Maximum simulation (blue crosses). The dashed red, green, and blue lines are the linear best fits in the 2XCO2, 6Kyr, and LGM runs, respectively. The dashed black line is the linear best fit to all experiments. The filled boxes are the ensemble mean of each simulation. (bottom) As at top, but for change in annual mean precipitation centroid (PCent) vs change in tropical SST gradient (?SST).
We introduce the outcome all over all the about three pressuring experiments here, following next analyze new 2XCO
(top) Change in annual mean precipitation centroid vs change in cross-equatorial heat transport in the atmosphere in the 2XCO2 simulations (each red cross is a different ensemble member), 6000 years before present simulations (green crosses), and Last Glacial Maximum simulation (blue crosses). The dashed red, green, and blue lines are the linear best fits in the 2XCO2, 6Kyr, and LGM runs, respectively. The dashed black line is the linear best fit to all experiments. The filled boxes are the ensemble mean of each simulation. (bottom) As at top, but for change in annual mean precipitation centroid (PPenny) vs change in tropical SST gradient (?SST).
We present the outcomes all over all the three forcing tests here, then then get acquainted with the latest 2XCO
(top) Change in annual mean precipitation centroid vs change in cross-equatorial heat transport in the atmosphere in the 2XCO2 simulations (each red cross is a different ensemble member), 6000 years before present simulations (green crosses), and Last Glacial Maximum simulation (blue crosses). The dashed red, green, and blue lines are the linear best fits in the 2XCO2, 6Kyr, and LGM runs, respectively. The dashed black line is the linear best fit to all experiments. The filled boxes are the ensemble mean of each simulation. (bottom) As at top, but for change in annual mean precipitation centroid (PCent) vs change in tropical SST gradient (?SST).