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badhatharry 11-19-2011 02:16 PM

new definition
 
of climate change.

"Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use."

instead of:

“a change of climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods.”

Starwatcher162536 12-01-2011 01:21 AM

Re: new definition
 
And?

bjkeefe 12-05-2011 04:06 PM

Re: new definition
 
Quote:

Originally Posted by Starwatcher162536 (Post 233107)
And?

Here's an and: "New approach to determining human impact on climate gives same answer." An especially worrisome bit (emph. added):

Quote:

Their ["researchers from the Institute for Atmospheric and Climate Science at ETH in Switzerland," whose "paper published this week in Nature Geoscience"] results showed that, between 1950 and 2004, the increasing concentration of carbon dioxide in the atmosphere has added a total of about 9 x 1023 joules of energy to the global energy balance. Other greenhouse gases have added another 7 x 1023 joules. In contrast, changes in solar activity added about 2 x 1023 (and the authors note that their calculated solar contribution is likely to be overestimated). On the flip side, approximately two-thirds of that added energy was offset by the cooling effects of aerosol emissions.

That means that most of the effect of anthropogenic greenhouse gas emissions has been masked by aerosols, without which we would have seen even greater warming. But those are just the current dynamics; while the residence time of aerosols in the atmosphere is fairly short, CO2 hangs around for a very long time. As the authors write, "The warming induced by CO2 will also persist for at least a thousand years as a result of the slow ocean carbon uptake, far longer than the warming from most other forcing agents."

This interplay leads to a sort of trap—aerosols will continue to mask some portion of warming until fossil fuel use seriously declines, at which point the full CO2 forcing will start to be felt.

By looking at the temperature trend associated with this time period, the authors conclude, "Our results show that it is extremely likely [>95 percent confidence] that at least 74 percent of the observed warming since 1950 was caused by anthropogenic radiative forcings, and less than 26 percent by unforced internal variability” such as oceanic oscillations. If you’re wondering where that leaves natural forcings, they calculate that solar activity is only responsible for about 0.07°C of the warming since 1950.
That bolded part reminded me of an article I saw a day or two ago: "Carbon Emissions Show Biggest Jump Ever Recorded."


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