A look at weather extremes and the big-picture climate connections.

Explaining Explosion of Daily Record Highs Easy as Pie

As the climate has warmed during the past several decades, there has been a growing imbalance between record daily high temperatures in the contiguous U.S. and record daily lows. A study published in 2009 found that rather than a 1-to-1 ratio, as would be expected if the climate were not warming, the ratio has been closer to 2-to-1 in favor of warm temperature records during the past decade (2000-2009). This finding cannot be explained by natural climate variability alone, the study found, and is instead consistent with global warming.

When you look at individual years, the imbalance can be more stark. For example, through late June 2012, daily record highs were outnumbering record daily lows by a ratio of 9-to-1.The study used computer models to project how the records ratios might shift in future decades as the amount of greenhouse gases in the air continues to increase. The results showed that the ratio of daily record highs to daily record lows in the lower 48 states could soar to 20-to-1 by mid-century, and 50-to-1 by 2100.

The shifting odds in favor of more daily record high temperatures being set compared to daily record low temperatures. Click on the image for a larger version. Credit: Climate Central.

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By Middleway (Earthling)
on July 16th, 2012

Our first scientific warning about CO2 induced global warming came in the 1960s. Ever since, the predictions have been confirmed and substantiated over the last 50 years. When one realizes that it took 300 years to accept that the Earth revolves around the Sun, and after 150 years evolution is still not universally accepted, one wonders how long it will take to accept human-induced global warming? It looks like it will take many more deaths and suffering (from severe weather) before the public will stop listening to the fossil fuel industry propaganda of doubt. Such a shame and disaster.

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By Richard George (Eugene, Oregon)
on July 18th, 2012

As a meteorologist, I find the most compelling evidence of global warming was a finding by a scientist whose views were
suppressed by big business for obvious reasons. He found pronounced warming in the troposphere compared to the
stratosphere. Natural warming by the sun would show a heat increase in both. There’s no question that these views are
fought by large corporations who benefit financially from avoiding “green measures” like limiting carbon dioxide emissions.

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By Anteaus (UK)
on July 19th, 2012

@Richard George: The claim that greater tropospheric warming should be an indication of AGW’s effect seems to be at odds with previous claims made by AGW proponents, namely that whilst the effect of CO2 at ground level is saturated, its greenhouse effect in rarified air at high altitude is not saturated and can therefore be increased by human activity. If that were the case, then the CO2-enriched stratosphere would tend to warm through increased absorbtion/scattering of inbound thermal infrared from the sun. The fact that, as you say, we do not see this happening suggests that the theory is incorrect, does it not?

Bulk gases are not black bodies, and hence can only warm by way of conduction from the surface, convection or molecular resonance (greenhouse effect) The math shows that in dense lower air, CO2-absorbtion band IR leaving the surface is intercepted within a few tens of metres of the surface. Thereafter, any warming of higher altitudes is due principally to convection currents. The stratosphere is significantly colder because the convection currents rarely reach that high. Thus, using basic non-AGW mechanisms, an increase in solar output would principally warm the lower atmosphere. A change in cloud cover might have similar effects. If the simple explanation makes sense, it is probably the right explanation.

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By Bud Peterson (Laramie, WY 82070)
on July 22nd, 2012

Well, I don’t know what proponents you are referring to.  Theory tells us that the atmosphere is heated from the bottom because the air is transparent to light, so the energy penetrates to the surface and is intercepted there.  The heated ground then emits the energy as infra red.  Also, carbon dioxide is heavier than air, so it tends to remain at lower altitudes.  As far as the infra-red being intercepted—what happens to that energy when it is absorbed?  It is converted to heat, thus warming the lower atmosphere.  Being warmed, the lower atmosphere re-emits it as infra-red.  This infra-red is emitted in every direction, so some of it goes downward, re-heating the ground.  Some is emitted upward, toward outer space, but it may be intercepted by the greenhouse effect.

Also,the primary reason that the upper atmosphere is colder than the lower, besides the fact that it is heated from below, is the adiabetic lapse rate:  as air rises due to convection, it expands because the pressure decreases.  As it expands, it does work and therefore is cooled, due to the first law of thermodynamics.

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