Arctic sea ice maximum reached, melt starts

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Arctic winter sea ice extent reached its maximum on March 31st, the latest date since satellite records began in 1979 according to the latest sea ice update from the National Snow and Ice Data Centre. The maximum extent was 15.25 million square kilometers. The NASA image above shows the ice extent on March 6th, before the late month growth spurt caused by a cold spell in the Bering and Barents seas. This late season ice is unlikely to have much impact on summer minimum, as it is thin and will melt rapidly as temperatures rise. Click on the image to get to a NASA animation of the winter ice season (not available on Youtube, or I would have posted it).

The NSIDC points out that a critical factor is the age and thickness of the ice as it heads into the summer melt season. The video below explains why, and how NASA is running a series of flights over the Arctic, the IceBridge campaign, to replace the thickness data lost with the ending of the first ICEsat mission. A new satellite won’t fly until 2013. The flights are already generating some fascinating imagery — I’ll be keeping an eye on their Twitter feed for more.

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Great balls of… air

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Two images of the day: above — the picture says it all. Doesn’t look like much, does it? [via Ecohustler, h/t @Revkin]. And below, a NASA photograph from the International Space Station showing what that thin skin of air looks like in situ. Note the large cumulonimbus clouds casting shadows, especially the one left of centre, which looks as though it’s bumped into the tropopause. [h/t In It For The Gold]

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Hansen: it can be cold in a warming world.

“If it’s that warm, how come it’s so darned cold?” is the heading James Hansen has given to a recently finalised essay circulated to his email list. In more sober terms he subtitles it Regional Cold Anomalies within Near-Record Global Temperature

The essay explains how the NASA Goddard Institute for Space Studies (GISS) goes about analyzing global temperature change, using electronic receipt of data from three sources: (1) weather data for several thousand meteorological stations, (2) satellite observations of sea surface temperature, and (3) Antarctic research station measurements. And for those who might suggest that there’s secret manipulation going on Hansen makes it clear that the data is available for others who want to use it:

 

“Although the three input data streams that we use are publicly available from the organizations that produce them, we began preserving the complete input data sets each month in April 2008. These data sets, which cover the full period of our analysis, 1880-present, are available to parties interested in performing their own analysis or checking our analysis. The computer program used in our analysis can be downloaded from the GISS web site.”

The results are that 2009 tied (with 1998, 2002, 2003, 2006 and 2007 – differences too close to matter) as the second warmest year in the 130 years of global instrumental temperature record.  The warmest was 2005.  Hansen discusses the variance of the GISS figures with the Hadley Centre (HadCRUT) which has 1998 as the warmest year, and which has been used so frequently to support claims that the globe since 1998 is now cooling. After careful comparison he concludes that the differences that have developed between the GISS and HadCRUT global temperatures are due primarily to the extension of the GISS analysis into regions that are excluded from the HadCRUT analysis. He expresses a reasonable degree of confidence in the GISS preference for 2005. Over the decade the conclusion is easier: the world has become warmer, not cooler.

What about that cold 2009 December?  There was an unusual exchange of polar and mid-latitude air in the northern hemisphere, related to the most extreme Arctic Oscillation since the 1970s. His conclusion is that December 2009 was a highly anomalous month. High pressure in the polar region can be described as the “cause” of the extreme weather. There is no apparent basis for expecting frequent repeat occurrences of December 2009 conditions, though high winter variability including cold snaps will surely continue.

Further discussion of seasonal temperature anomalies leads to the observation that the change in the probability that the seasonal mean temperature at any given location will fall in the category that was defined as unusually warm during 1951-1980 has increased from 30 percent during that period to about 60 percent today. This will be illustrated in an upcoming publication.

The bottom line?

“The Earth has been in a period of rapid global warming for the past three decades. The assertion that the planet has entered a period of cooling in the past decade is without foundation. On the contrary, we find no significant deviation from the warming trend of the past three decades.”

I haven’t attempted to offer any of the detail with which Hansen builds his conclusions, but can report it as readily accessible to the lay person prepared to give it reasonably patient attention. The essay is another example of his skill in communicating serious science to non-scientists and of his laudable willingness to do so.

His preliminary remarks are worth separate attention. He notes that scientists reporting global warming have come under attack for a supposed conspiracy to manufacture evidence of global warming. Vicious personal messages are sent to the principal scientists almost daily.

“The spiral into an almost surrealistic situation with ad hominem attacks on scientists may have originated in part with vested interests who do not want society to address climate change. But there is more than that – including honest, wishful thinking that climate change is not really happening. But wishing does not alter facts.”

He stoutly supports the work of scientists:

“The scientific method practically defines integrity… All scientists make honest mistakes, but the scientific method is designed to correct them. The skeptical nature of the scientific method causes conclusions to be reexamined as new data appears. Cases of deliberate fudging of data, of scientific fraud, are so rare that these infrequent episodes live in infamy for decades and even centuries.”

He knows of no cases of fraud in analyses of global temperature measurements. In the face of unfounded accusations “our best approach is simply to continue to report our scientific results as clearly as possible.”

He thinks that most of the public continue to respect scientists for what they do and how they do it. I hope he’s right. Sometimes I think the forces of denial have taken on the aspect of a rampaging demonic power, against which the forces of quiet reason are for the time being ineffectual.

…Keep out of the kitchen

It appears that Ian Wishart is back on the climate beat, with a couple of posts in the last week attacking Hot Topic. One goes so far as to accuse me of incompetence and dishonesty, which is a bit rich coming from someone who was threatening to sue me for libel a few months ago… Anyway, his latest offering attempts to chastise me for stating in a comment that global temperatures were not falling. That gives me a welcome opportunity to post on the subject and introduce a nifty little gadget programmed by a Hot Topic reader. Here’s Wishart:

Virtually all the major datasets are now acknowledging atmospheric warming has slowed to a crawl or stopped over the past ten years, and even some leading climate alarmists scientists are publicly suggesting we’ve entered a climate shift and may not see warming return for a further decade or more. The data clearly shows temperature anomalies trending down despite CO2 emissions rising:

He appends a graph of UAH monthly temperature anomalies from 2002 to some point earlier this year, with a descending trend line. Lo and behold, “cooling”!

Continue reading “…Keep out of the kitchen”

A beginner’s guide to the importance of Arctic sea ice

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In this beginner’s guide Tom Wagner, NASA’s cryosphere programme manager, outlines why studying Arctic sea ice is important, illustrating his talk with some great graphics. Meanwhile, the NSIDC has announced the final figures for September’s sea ice minimum:

The average ice extent over the month of September, a reference comparison for climate studies, was 5.36 million square kilometers (2.07 million square miles). This was 1.06 million square kilometers (409,000 square miles) greater than the record low for the month in 2007, and 690,000 square kilometers (266,000 square miles) greater than the second-lowest extent in 2008. However, ice extent was still 1.68 million square kilometers (649,000 square miles) below the 1979 to 2000 September average.

NSIDC scientist Walt Meier thinks there may be some hope of “stabilising” the ice after recent heavy losses:

We’ve preserved a fair amount of first-year ice and second-year ice after this summer compared to the past couple of years. If this ice remains in the Arctic through the winter, it will thicken, which gives some hope of stabilizing the ice cover over the next few years. However, the ice is still much younger and thinner than it was in the 1980s, leaving it vulnerable to melt during the summer.

But will there be a longer term recovery back towards the sort of ice cover seen before 2000? The NSIDC team doesn’t think so.

NSIDC lead scientist Ted Scambos said, “A lot of people are going to look at that graph of ice extent and think that we’ve turned the corner on climate change. But the underlying conditions are still very worrisome.”

After a couple of cool summers, one wonders what impact another warm year might do to the ice. As ever, I shall be watching next year with great interest…