originally posted by: ArchPlayer
And here I heard Greenland was going back to being Green when the ice melted a few years ago.
What was the Chicago July record BTW?
Great post OP. Chicago has had relatively mild winters since the blizzard of 1999. Actually, its been seasonably warm since then. No one can actually say Chicago had a crushing winter like 20 years ago because it hasn't happen. Keep in mind the summers have also been exceptionally cooler in the last 15 years as well. Nothing like the sweltering heat of the early 90s. Back in the 1980s man, those were some COLD ASS Winters. Windchill would be 80 below zero easily in December. We use to keep food on the back porch it was so cold and it would keep quite nicely.
Chicago has always had 8 months of winter and 4 months of summer. No spring or fall really as fast as the temps plummet. But it has been cool summers though.
originally posted by: bbracken677
I read an interesting piece by an Australian physicist who claims he can show how atmospheric co2 does not, indeed, behave as claimed (greenhouse gas) which would explain a lack of correlation between rise in co2 and temperatures historically.
The average sea level pressure is around 1013 mbar. If you live at a higher altitude the pressure will be less. Your barometer at 100 m above sea level will read about 12 mbar less. Pressure is a direct measurement of how much atmospheric mass there is above your head per square meter. The ideal gas law can be written PV = RT where P is the pressure (Pascal), V is the volume (m3), R is the gas constant (Joule/K) and T is the average temperature (over some days). Let us now calculate the temperature in a 1 m3 volume at any height. Hence T = P/R, T is proportional to P and P is known from observation to decrease with increasing altitude. It follows that the average T has to decrease with altitude. This decrease from the surface to the average infrared emission altitude around 4000 m is 33oC. It will be about the same even if we increase greenhouse gases by 100%. This is a consequence of the ideal gas law, a natural law which politicians cannot change, but unscrupulous scientists can twist.
Over the last 400,000 years the natural upper limit of atmospheric CO2 concentrations is assumed from the ice core data to be about 300 ppm. Other studies using proxy such as plant stomata, however, indicate this may closer to the average value, at least over the last 15,000 years. Today, CO2 concentrations worldwide average about 380 ppm. Compared to former geologic periods, concentrations of CO2 in our atmosphere are still very small and may not have a statistically measurable effect on global temperatures. For example, during the Ordovician Period 460 million years ago CO2 concentrations were 4400 ppm while temperatures then were about the same as they are today.
Do rising atmospheric CO2 concentrations cause increasing global temperatures, or could it be the other way around? This is one of the questions being debated today. Interestingly, CO2 lags an average of about 800 years behind the temperature changes-- confirming that CO2 is not the cause of the temperature increases. One thing is certain-- earth's climate has been warming and cooling on it's own for at least the last 400,000 years, as the data below show. At year 18,000 and counting in our current interglacial vacation from the Ice Age, we may be due-- some say overdue-- for return to another icehouse climate!
"Twentieth century global warming did not start until 1910. By that time CO2 emissions had already risen from the expanded use of coal that had powered the industrial revolution, and emissions only increased slowly from 3.5gigatonnes in 1910 to under 4gigatonnes by the end of the Second World War. It was the post war industrialization that caused the rapid rise in global CO2 emissions, but by 1945 when this began, the Earth was already in a cooling phase that started around 1942 and continued until 1975. With 32 years of rapidly increasing global temperatures and only a minor increase in global CO2 emissions, followed by 33 years of slowly cooling global temperatures with rapid increases in global CO2 emissions, it was deceitful for the IPCC to make any claim that CO2 emissions were primarily responsible for observed 20th century global warming." (Norm Kalmanovitch).
There has historically been much more CO2 in our atmosphere than exists today. For example, during the Jurassic Period (200 mya), average CO2 concentrations were about 1800 ppm or about 4.7 times higher than today. The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Cambrian Period, nearly 7000 ppm -- about 18 times higher than today. The Carboniferous Period and the Ordovician Period were the only geological periods during the Paleozoic Era when global temperatures were as low as they are today. To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age while at the same time CO2 concentrations then were nearly 12 times higher than today-- 4400 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.
Throughout the Carboniferous Period, continental drift was rearranging most (but not all) of the Earth's landmasses into a single supercontinent stretching from the south polar region to the north polar region. Although the precise mechanisms involved are still a matter of debate this appears to cause regional humidity changes and redistribution of ocean currents which in turn promote ice accumulation and glacier formation over the earth's polar continents. These glacial ice caps grow larger during periods of reduced solar input, and because ice caps are very good solar reflectors this tended to accelerate and perpetuate cyclical relapses to global cooling. Basically, Earth undergoes alternating periods of ice ages and warming whenever a continuous continental landmass extends from one polar region to the other while at the same time there exists a large polar continent capable of supporting thick ice accumulations. These conditions existed 300 million years ago during the Carboniferous Period as they do for the Earth today. However for most of geologic history the distribution of the continents across the globe did not satisfy this criteria. Continental drift continually rearranges the continents, moving at rates of only a few centimeters per year.
Recent discussion of the Shakun et al. (Nature 2012) paper has illuminated issues in its presentation of the history of CO2 versus temperature (commentaries here, here, here, and here). In addition to those investigations, another helpful approach may be to take a step back and cross-check with other sources.
In general, does CO2 correlate with temperature in climate history?
The answer is often yes on “medium” timescales, but no on “short” timescales and also no on the very longest timescales of all. If one looks at all three timescales, overall observations are consistent with temperature rise causing the oceans to release part of their dissolved CO2 after substantial lag time, yet not consistent with CO2 being the primary driver of climate. Over the past few hundred thousand years of ice core data, a “medium” time scale in this sense, CO2 superficially appears to change in step with temperature if a graph is so zoomed out as to not show sub-millennial time scales well:
the northern ice cap ice has been growing
That would be sea ice and attributeable to wind patterns, not cooling. How's the land ice holding up?
I think antarctica is like 18% greater ice coverage than a few years ago.