Post by william on Mar 15, 2010 1:08:55 GMT
Socold,
The paper you quote is a review paper that has no scientific observations (data) or evidence to support the hypothesis that the planet’s response to a change in forcing is positive rather than negative.
It's a review of climate sensitivity estimates, it isn't supposed to contain data. The papers it cites contain the data. Those estimates form the evidence for climate sensitivity and many of those estimates are based on observations (data).
The data is in the studies it references. For example estimates based on the instrumental record use data from the instrumental record. Studies estimating climate sensitivity from the last glacial maximum use data from ice cores.
The papers you quote make assume positive feedback based on partial correlation.
Lindzen's analysis uses actual measurement of ocean surface temperature and actual measurement of top of the atmosphere radiation. Lindzen's conclusion is based on analysis not assumptions.
The IPCC specifically notes the models do not model cloud cover.
Lindzen's analysis uses actual measurement of ocean surface temperature and actual measurement of top of the atmosphere radiation. Lindzen's conclusion is based on analysis not assumptions.
The IPCC specifically notes the models do not model cloud cover.
Or perhaps it's the high amount of co2 in atmosphere back then. I do recall an argument complaining that in the distant past co2 was very high but temperature was as today. Well the faint sun would explain that would it not?
CO2 levels were more than 3 times current levels in the past. Back 500 million years or so co2 levels were a few thousand ppm.
Socold, CO2 would need to be 3 Bar to explain the faint sun paradox. Atmospheric pressure would need to be three times current atmospheric pressure with the majority of the atmosphere CO2. That is physically not possible based on the source of CO2 and does not match chemistry of the ancient sediments.
Comment: As atmospheric pressure increases gases start to act like liquids and the quantum levels merge. Venus has an atmospheric pressure that is 90 times the earth's which explains its high temperature.
P.S. You did not listen to Lindzen's lecture.
Comment: As atmospheric pressure increases gases start to act like liquids and the quantum levels merge. Venus has an atmospheric pressure that is 90 times the earth's which explains its high temperature.
P.S. You did not listen to Lindzen's lecture.
I am interested to know what period this was.
There was some interesting news recently about snowball earth and the possibility of the planet being largely covered by ice.
www.sciencedaily.com/releases/2010/03/100304142228.htm
Given the decrease in absorbed solar radiation if the earth is largely covered in ice, how do you get the earth out of such a locked state if feedbacks are negative?
Positive feedback makes it more difficult to get out of low or high state, not easier. Positive feedback makes systems unstable.
On the contrary - the review paper I posted shows the distribution of paleoclimate data based estimates - they overwhelmingly show positive feedback. See the part "proxy data from millions of years ago" and "last glacial maximum, data" for example.
Positive feedback just amplifies any change. It doesn't keep going, it just peaks higher. With higher feedback the glacial/interglacial transition could have been 10C globally rather than about 5C for example. With lower it could have been just 2C.
There is no indication from current or past climatic temperatures of positive feedback. Systems that have positive feedback oscillate. As I said, man made system are designed with negative system as positive systems are unstable. A large volcanic eruption could result in the start of glacial period. That is not what is observed.
Lindzen's paper is based on observation and analysis. The planet's response to an increase in forcing is negative. If the planet's response is zero everyone agrees the planet will warm 1.2C. To get the an increase in temperature of 1.5C to 5C the planet's response must be massively positive. There is no scientific data to support massively positive feedback.
Evidentially there is or all those studies would have managed to rule it out.
Listen to Lindzen's lecture. AWG is agenda driven not science driven.
This paper supports Lindzen's paper's conclusion.
ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F2009JCLI3461.1
Why Hasn't the Earth Warmed as Much as Expected? Stephen E. Schwartz, Robert J. Charlson, Ralph A. Kahn, John A. Ogren, Henning Rodhe Issued January 19th, 2010
The observed increase in global mean surface temperature (GMST) over the industrial era is less than 40% of that expected from observed increases in long-lived greenhouse gases together with the best-estimate equilibrium climate sensitivity given by the 2007 Assessment Report of the Intergovernmental Panel on Climate Change. Possible reasons for this warming discrepancy are systematically examined here. The warming discrepancy is found to be due mainly to some combination of two factors: the IPCC best estimate of climate sensitivity being too high and/or the greenhouse gas forcing being partially offset by forcing by increased concentrations of atmospheric aerosols; the increase in global heat content due to thermal disequilibrium accounts for less than 25% of the discrepancy, and cooling by natural temperature variation can account for only about 15%. Current uncertainty in climate sensitivity is shown to preclude determining the amount of future fossil fuel CO2 emissions that would be compatible with any chosen maximum allowable increase in GMST; even the sign of such allowable future emissions is unconstrained. Resolving this situation, by empirical determination of Earth's climate sensitivity from the historical record over the industrial period or through use of climate models whose accuracy is evaluated by their performance over this period is shown to require substantial reduction in the uncertainty of aerosol forcing over this period.
The observed increase in global mean surface temperature (GMST) over the industrial era is less than 40% of that expected from observed increases in long-lived greenhouse gases together with the best-estimate equilibrium climate sensitivity given by the 2007 Assessment Report of the Intergovernmental Panel on Climate Change. Possible reasons for this warming discrepancy are systematically examined here. The warming discrepancy is found to be due mainly to some combination of two factors: the IPCC best estimate of climate sensitivity being too high and/or the greenhouse gas forcing being partially offset by forcing by increased concentrations of atmospheric aerosols; the increase in global heat content due to thermal disequilibrium accounts for less than 25% of the discrepancy, and cooling by natural temperature variation can account for only about 15%. Current uncertainty in climate sensitivity is shown to preclude determining the amount of future fossil fuel CO2 emissions that would be compatible with any chosen maximum allowable increase in GMST; even the sign of such allowable future emissions is unconstrained. Resolving this situation, by empirical determination of Earth's climate sensitivity from the historical record over the industrial period or through use of climate models whose accuracy is evaluated by their performance over this period is shown to require substantial reduction in the uncertainty of aerosol forcing over this period.