Why? Well, warm periods have occured in the past, and if not the medieval period, then probably the last interglacial (120,000 years ago), certainly the Pliocene (3 million years ago), without question the (Eocene 50 million years), and in particular the Paleocene-Eocene Thermal Maximum (55 million years ago), and so on. Current theories of climate change do not rely on whether today’s temperatures are ‘unprecedented’. Instead they examine the physical causes of climate change and match up what we know about their physical effects and time history and see which of the multiple drivers or combination can best explain the observations. For the last few decades, that is quite clearly the rise in greenhouse gases, punctuated by the occasional volcano and mitigated slightly by the concomittant rise in particulate pollution.
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Saturday, April 04, 2015
In 2006, Gavin Schmidt claimed that greenhouses gases "quite clearly" caused the warming over the last few decades
RealClimate: Medieval warmth and English wine
Existing data and rudimentary math prove that CO2 has no significant effect on climate.
ReplyDeleteExisting data includes temperature and CO2 determined from Vostok, Antarctica ice cores for several glacial and inter-glacial periods.
Temperature and CO2 (Berner, 2001) for the entire Phanerozoic eon (about 542 million years) are graphed at http://www.geocraft.com/WVFossils/Carboniferous_climate.html ).
A forcing must act for a duration to produce a temperature change. For example, a burner under a block of iron will cause the temperature of the block of iron to increase as long as the net forcing is positive. The burner is a positive forcing while radiation and convection from the block provide a negative forcing. The temperature asymptotically approaches a new steady-state temperature as the positive and negative forcings approach cancelling each other. The temperature change of the block at any time equals a scale factor times the time-integral of the net forcing up to that time.
If the temperatures at the beginning and end of the duration are equal, and the time-integral of the forcing (or the time-integral with respect to an average forcing, or the time-integral with respect to a threshold forcing) is not zero, the scale factor must be zero. Periods of equal beginning and ending temperatures exist in the data records. If beginning and end temperatures are equal, but the time-integral of the CO2 level (or difference) is not zero, the scale factor must be zero and thus CO2 can have no significant effect on average global temperature.
Climate sensitivity, (the increase in AGT due to doubling of CO2) is therefore not significantly different from zero.
Additional proof showing that CO2 has no significant effect on climate and identification of the two factors that do are disclosed at http://agwunveiled.blogspot.com