<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;"><DIV>Global Warming takes a break?</DIV>
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<DIV>Its because Obama is President. :P</DIV>
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<DIV>Donovan Arnold<BR><BR>--- On <B>Wed, 10/14/09, Ted <SPAN>Moffett</SPAN> <I><starbliss@gmail.com></I></B> wrote:<BR></DIV>
<BLOCKQUOTE style="BORDER-LEFT: rgb(16,16,255) 2px solid; PADDING-LEFT: 5px; MARGIN-LEFT: 5px"><BR>From: Ted Moffett <starbliss@gmail.com><BR>Subject: [Vision2020] RealClimate.org, 10/6/2009: Climate Change Slowing or Stopping?: 371 Responses!<BR>To: "Moscow Vision 2020" <vision2020@moscow.com><BR>Date: Wednesday, October 14, 2009, 12:02 PM<BR><BR>
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<DIV><A href="http://www.realclimate.org/index.php/archives/2009/10/a-warming-pause/#more-1265" rel=nofollow target=_blank>http://www.realclimate.org/index.php/archives/2009/10/a-warming-pause/#more-1265</A></DIV>
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<H3 id=post-1265 class=storytitle>A warming pause?</H3>
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<LI><A title="View all posts in skeptics" href="http://www.realclimate.org/index.php/archives/category/communicating-climate/skeptics/" rel=nofollow target=_blank><FONT size=2>skeptics</FONT></A></LI></UL>— stefan @ 6 October 2009 </DIV>
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<DIV class=meta>Stefan Rahmstorf's bio:</DIV>
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<DIV class=meta><A href="http://www.realclimate.org/index.php/archives/2004/12/stefan-rahmstorf/" rel=nofollow target=_blank>http://www.realclimate.org/index.php/archives/2004/12/stefan-rahmstorf/</A></DIV>
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<DIV class=meta>The blogosphere (and not only that) has been full of the “global warming is taking a break” meme lately. Although we have <A href="http://www.realclimate.org/index.php/archives/2008/12/2008-temperature-summaries-and-spin/" rel=nofollow target=_blank><FONT color=#66aa55>discussed</FONT></A> <A href="http://www.realclimate.org/index.php/archives/2008/11/mind-the-gap/" rel=nofollow target=_blank><FONT color=#66aa55>this</FONT></A> <A href="http://www.realclimate.org/index..php/archives/2008/04/model-data-comparison-lesson-2/" rel=nofollow target=_blank><FONT color=#66aa55>topic</FONT></A> <A href="http://www.realclimate.org/index.php/archives/2008/01/uncertainty-noise-and-the-art-of-model-data-comparison/" rel=nofollow target=_blank><FONT color=#66aa55>repeatedly</FONT></A>, it is perhaps worthwhile reiterating two key points about the alleged pause here.</DIV>
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<DIV>(1) This discussion focuses on just a short time period – starting 1998 or later – covering at most 11 years. Even under conditions of anthropogenic global warming (which would contribute a temperature rise of about 0.2 ºC over this period) a flat period or even cooling trend over such a short time span is nothing special and has happened repeatedly before (see 1987-1996). That simply is due to the fact that short-term natural variability has a similar magnitude (i.e. ~0.2 ºC) and can thus compensate for the anthropogenic effects. Of course, the warming trend keeps going up whilst natural variability just oscillates irregularly up and down, so over longer periods the warming trend wins and natural variability cancels out.</DIV>
<DIV>(2) It is highly questionable whether this “pause” is even real. It does show up to some extent (no cooling, but reduced 10-year warming trend) in the Hadley Center data, but it does not show in the GISS data, see Figure 1. There, the past ten 10-year trends (i.e. 1990-1999, 1991-2000 and so on) have all been between 0.17 and 0.34 ºC per decade, close to or above the expected anthropogenic trend, with the most recent one (1999-2008) equal to 0.19 ºC per decade – just as predicted by IPCC as response to anthropogenic forcing. </DIV>
<DIV><A href="http://www.realclimate.org/wp-content/uploads/GISStrends.jpg" rel=nofollow target=_blank><IMG alt="GISS temperature trends" src="http://www.realclimate.org/wp-content/uploads/GISStrends.jpg"></A> </DIV>
<DIV><EM><STRONG>Figure 1. </STRONG>Global temperature according to NASA GISS data since 1980. The red line shows annual data, the larger red square a preliminary value for 2009, based on January-August. The green line shows the 25-year linear trend (0.19 ºC per decade). The blue lines show the two most recent ten-year trends (0.18 ºC per decade for 1998-2007, 0.19 ºC per decade for 1999-2008) and illustrate that these recent decadal trends are entirely consistent with the long-term trend and IPCC predictions. Even the highly “cherry-picked” 11-year period starting with the warm 1998 and ending with the cold 2008 still shows a warming trend of 0.11 ºC per decade (which may surprise some lay people who tend to connect the end points, rather than include all ten data points into a proper trend calculation).</EM><BR><SPAN id=more-1265></SPAN><BR>Why do these two surface temperature data sets differ over recent years? We <A
href="http://www.realclimate.org/index.php/archives/2008/11/mind-the-gap/" rel=nofollow target=_blank><FONT color=#66aa55>analysed this</FONT></A> a while ago here, and the reason is the “hole in the Arctic” in the Hadley data, just where recent warming has been greatest.</DIV>
<DIV><A href="http://www.realclimate.org/wp-content/uploads/ncepawrming.gif" rel=nofollow target=_blank><IMG alt="Mean temperature difference between the periods 2004-2008 and 1999-2003" align=right src="http://www.realclimate.org/wp-content/uploads/rcanim.gif" width=450></A><BR><EM><STRONG>Figure 2.</STRONG> The animated graph shows the temperature difference between the two 5-year periods 1999-2003 and 2004-2008. The largest warming has occurred over the Arctic in the past decade and is missing in the Hadley data.</EM></DIV>
<DIV>If we want to relate global temperature to global forcings like greenhouse gases, we’d better not have a “hole” in our data set. That’s because global temperature follows a simple planetary heat budget, determined by the balance of what comes in and what goes out.. But if data coverage is not really global, the heat budget is not closed. One would have to account for the heat flow across the boundary of the “hole”, i.e. in and out of the Arctic, and the whole thing becomes ill-determined (because we don’t know how much that is). Hence the GISS data are clearly more useful in this respect, and the supposed pause in warming turns out to be just an artifact of the “Arctic hole” in the Hadley data – we don’t even need to refer to natural variability to explain it.</DIV>
<DIV>Imagine you want to check whether the balance in your accounts is consistent with your income and spendings – and you find your bank accounts contain less money than you expected, so there is a puzzling shortfall.. But then you realise you forgot one of your bank accounts when doing the sums – and voila, that is where the missing money is, so there is no shortfall after all. That missing bank account in the Hadley data is the Arctic – and we’ve <A href="http://www.realclimate.org/index.php/archives/2008/11/mind-the-gap/" rel=nofollow target=_blank><FONT color=#66aa55>shown</FONT></A> that this is where the “missing warming” actually is, which is why there is no shortfall in the GISS data, and it is pointless to look for explanations for a warming pause.</DIV>
<DIV>It is noteworthy in this context that despite the <A href="http://www.pmodwrc.ch/pmod.php?topic=tsi/composite/SolarConstant" rel=nofollow target=_blank><FONT color=#66aa55>record low</FONT></A> in the brightness of the sun over the past three years (it’s been at its faintest since beginning of satellite measurements in the 1970s), a number of <A href="http://www.ncdc.noaa.gov/sotc/" rel=nofollow target=_blank><FONT color=#66aa55>warming records</FONT></A> have been broken during this time. March 2008 saw the warmest global land temperature of any March ever recorded in the past 130 years. June and August 2009 saw the warmest land and ocean temperatures in the Southern Hemisphere ever recorded for those months. The global ocean surface temperatures in 2009 broke all previous records for three consecutive months: June, July and August. The years 2007, 2008 and 2009 had the lowest summer Arctic sea ice cover ever recorded, and in 2008 for the first
time in living memory the Northwest Passage and the Northeast Passage were simultaneously ice-free. This feat was repeated in 2009. Every single year of this century (2001-2008) has been warmer than all years of the 20th Century except 1998 (which sticks out well above the trend line due to a strong El Niño event).</DIV>
<DIV>The bottom line is: the observed warming over the last decade is 100% consistent with the <A href="http://www.pik-potsdam.de/~stefan/update_science2007.html" rel=nofollow target=_blank><FONT color=#66aa55>expected anthropogenic warming trend</FONT></A> of 0.2 ºC per decade, superimposed with short-term natural variability. It is no different in this respect from the two decades before. And with an <A href="http://www.elnino.noaa.gov/" rel=nofollow target=_blank><FONT color=#66aa55>El Niño developing</FONT></A> in the Pacific right now, we wouldn’t be surprised if more temperature records were to be broken over the coming year or so.</DIV>
<DIV><STRONG>Update:</STRONG> We were told there is a <A href="http://www..agu.org/journals/pip/jd/2009JD012442-pip.pdf" rel=nofollow target=_blank><FONT color=#66aa55>new paper</FONT></A> by Simmons et al. in press with JGR that supports our analysis about the Hadley vs GISS trends (sorry, access to subscribers only).</DIV>
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<DIV>Vision2020 Post: Ted Moffett</DIV></DIV></DIV></DIV><BR>-----Inline Attachment Follows-----<BR><BR>
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