Wednesday, June 20, 2012

Report: Humans Are the Main Cause of Global Warming

A recently released report, published in the June 10 issue of the journal Nature Climate Change, and authored by Peter Gleckler et al, pinpoints humans as the dominant source of climate change-global warming. The research, based on monitoring of ocean warming over the past fifty years, is consistent with other climate models only if the models include the increases in greenhouse gases (mainly CO2) during the 20th century. Of course, it is precisely the 20th century that has been the century of maximal fossil fuel use.

Interestingly, the new research also confirms and reinforces the carbon isotope ratio results over centuries that I'd blogged about a year and a half ago, i.e.

As I quoted the late solar physicist John Eddy, in terms of his explanation of the data for that curve:

"The sharp upward spike at the modern end of the curve, representing a marked drop in relative radiocarbon, is generally attributed to anthropogenic causes—the mark of increased population and the Industrial Age. The burning of low radiocarbon fossil fuels- coal and oil- and the systematic burning off of the world’s forests for agriculture can be expected to dilute the natural C14/C12 ratio in the troposphere to produce an effect like the one shown, though a real increase in solar activity may be hidden under the curve

Now, in this work by Gleckler et al the connection to fossil fuel output is even more rigorously determined.
The researchers looked at the average temperature (heat content) of the upper layers of the ocean. As they noted:

The observed global average ocean warming (from the surface to 700 meters) is approximately 0.025 degrees Celsius per decade, or slightly more than 1/10th of a degree Celsius over 50 years.”

The sub-surface warming is somewhat less than that because of the slow transfer of surface warming to lower depths. They added:

Nevertheless, because of the ocean’s enormous heat capacity, the oceans likely account for more than 90 percent of the heat accumulated over the past 50 years as Earth has warmed.”

Recall from basic physics that the heat tied to a substance is: Q = mc (T' - T)

where m is the total mass (in this case the mass of all the oceans), c is the specific heat capacity in this case for water, or 4200 J/Kg C and the temperature difference is (T' - T). Thus, even if (T' - T) = 0.025 C, an evident small amount of warming, the total heat Q stored in the oceans is still massive by virtue of m being vast (about  1.4 x 10^21 kg, see, e.g.: Then the total heat stored is:

Q = (10^21 kg) (4200 J/kg C) (0.025 C) = 1. 4 x 10^23 J

which is an enormous quantity of heat!

A secondary refinement entailed the researchers using results from a large multi-model archive of control simulations (i.e. which don’t include the effects of humans, only natural variability), which they compared to simulations that included the effects of fossil fuel emissions during the 20th century. According to principal author Gleckler:

"By using a ‘multi-model ensemble,’ we were better able to characterize decadal-scale natural climate variability, which is a critical aspect of the detection and attribution of a human-caused climate change signal. What we are trying to do is determine if the observed warming pattern can be explained by natural variability alone,”

Gleckler concluded:

"Although we performed a series of tests to account for the impact of various uncertainties, we found no evidence that simultaneous warming of the upper layers of all seven seas can be explained by natural climate variability alone. Humans have played a dominant role.”

Meanwhile, in a special report on global warming in advance of the Rio Summit, The Economist (June 16, 2012) notes that Greenland's ice cap is "losing an estimated 200 gigatonnes of ice a year, enough to supply a billion people with water. "

If this should continue, and lead to a predicted 59 cm (24 in.) rise in sea level by the end of the century, it will prove catastrophic for many population centers abutting the oceans.

People also tend to forget or not process, as the article points out, that different regions of the planet undergo differing warming rates. Thus, while the 0.7 C global increase since 1951 is generally referred to, including by Deniers (since they regard it as 'tweedlee and tweedledum ' difference) the Arctic is rising much faster. In Greenland, for example, the rate is 1.5C since 1951. The report also envisages a possible 3- 6 C Arctic warming which would be catastrophic.

Amazingly, even as we head toward the next Rio Summit on Climate Change, the Denier-flat Earther brigade remains committed to its ideological delusions. See, for example, this editorial from the local rag:

This nincompoop editor even repeats the widely circulated canard that "temperatures have flattened", e.g.

"About 130 world leaders will gather in Rio de Janeiro, Brazil, this week to establish more rules, regulations and transfers of wealth, ostensibly to eradicate poverty and protect the environment.This is yet another U.N. attempt to advance its war against what first was demonized as “global warming,” then “climate change” when temperatures flattened out."

Since when? As The Economist notes:

"Six of the hottest years on record- going back to 1880- have occurred since 2004"

And this year also is on track to add to that. So how is this a "flattening out" unless The Gazelle editor means flattening out on the high temperature side? Even so, as The Economist reports "A 2 C increase in global mean temperatures appears inevitable".

That is certainly not a "flattening out"! But perhaps the flattened frontal lobes of  Flat Earthers process information in a flat way. Who knows?

What we do know is that there is very little potential for any temperatures flattening in the near future. Our biggest near term fear: all the carbon and methane-laden permafrost in the Arctic. If all that melts, we are all fucked....totally! As The Economist notes:

"According to an estimate made in 2009, terrestrial permafrost holds about 1.7 trillion tonnes of carbon....and underlying it may be another 0.8 trillion tonnes of methane."

The problem? If that methane is also released. Since "methane stays in the atmosphere 6-10 years before being oxidized but is 25 times more efficient than carbon dioxide at trapping heat."

Let us all hope the day of that permafrost methane release never arrives!

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