Weatherdem's Weblog

Bridging climate science, citizens, and policy

Climate Change Information Update

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A few items were made available recently that provide additional information regarding global climate change.

In the last month, much has been made about the cooling recording in January. Delayers have used this data to claim that there is global cooling, not warming going on. If only they didn’t react to every single datum that came out, they might be able to build a coherent argument. But let’s stick with the data, shall we? Both NASA and the Hadley Center‘s analysis show that global temperatures in 2007 remained high: NASA listed 2007 as the second warmest on record, behind 2005, and the Hadley center listed 2007 as the seventh warmest. And before someone comes along and tries to argue that the difference in rankings prove something, both centers’ data show a difference of less than 0.5C between the first and tenth warmest year. The point is that 2007 was among the warmest in the last 100+ years.

Which brings us to January of this year. Embedded within the 2007 temperature data is the following: it was actually characterized by a strong La Nina event. La Nina is the cooler portion of ENSO. That’s right: global temperatures, even under the influence of a major ocean temperature cooling phenomenon, were still among the warmest recorded: almost as warm as the extreme El Nino event of 1998. By January, the La Nina event was in its mature stage. Here’s where the delayers’ argument comes in: January 2008 was much cooler than January 2007. Instead of a +0.632C anomaly in Jan. 2007, Jan. 2008 had a +0.037C anomaly.

Hmm, that’s interesting. Anomaly compared to what? Every dataset they’re examining uses mid-20th century data as a baseline, which is fine, or doesn’t consider the entire globe, which isn’t fine. Temperature data at the poles are critical for understanding what the global change of temperature is doing. This is especially true when one realizes that most of the temperature changes we’ve recorded have occurred in the polar regions. Most mid-latitude locations haven’t recorded the same magnitude of warming that the poles have (normalized differences are very large at the poles, thus you’ll rarely, if ever, see delayers use them as a data source).

So if 2007 was among the warmest years recorded and a strong La Nina developed during the year, what kind of temperature anomalies will we see during the next strong El Nino? And what lame excuse will delayers come up with to try to explain it away?

In concert with the delayers’ misinterpretation of temperature data, they’re also saying that there is ‘record ice growth this winter’ in the Arctic. Of course, this has to mean global cooling, right? Not so much, actually. Remember that 2007 saw the greatest loss of Arctic sea ice in one year since measurements were recorded. Last year, over 2 million sq km of Northern Hemispheric Sea Ice disappeared. From that condition, it wouldn’t take much for record ice creation to occur, especially during a strong La Nina event. Indeed, that’s what the last portion of the graph shows. The largest message the graph shows is the long-term behavior of ice anomaly: further away from the mean in the negative direction.

Just as importantly, the condition of the ice should be taken into account. Okay, a large amount of ice has been created during this boreal winter. How has the long-term ice fared under recent conditions? As this picture demonstrates, things aren’t looking so good. Most of the ice in the Arctic has existed for about one year. This ice is less thick and saltier than the kind of ice that has a chance to grow for multiple years. The area of ice that has existed for three years or more is drastically reduced when compared to the 1985-2000 (Februaries) period. Even if 2008 isn’t as warm as it has been for the past 10 years, the ice that formed this winter likely won’t last long. Put another way, the increased area of sea ice this winter is due to recent weather conditions, while the decline in perennial ice reflects the longer-term warming climate trend and is a result of increased melting during summer and greater movement of the older ice out of the Arctic.

*****

It’s been very well documented that humans are the main culprit behind the recent changes in the state of the global climate. One of the things scientists and policy makers must come to grips with is setting the goal of CO2 concentrations in the atmosphere we wish to maintain. As one of James Hansen’s papers (pdf) illustrates, current CO2 concentrations are at 385ppm and are currently increasing at a rate of 2ppm/yr. Note that the rate itself is also increasing: we will likely see greater changes in concentration in the future.

Antarctica glaciated during the Cenozoic when CO2 concentrations were dropping and passed ~450ppm. Given the current rate of increase, we have about 30 years before we push through that value. If that rate increases, as is expected, concentrations will exceed 450ppm in less than 30 years. At which point, the planet would be ice free, as temperatures responded to CO2 levels. For comparison sake, sea levels during the Cenozoic were 200 feet higher. If we pass that threshold, how long would it take to decrease the CO2 concentrations? Decades to centuries.

The lesson here is easy: we have the scientific capability to slow, moderate, then decrease our release of CO2 into the Earth system. What we currently lack, and what delayers rejoice at, is the political will to do anything about it. The sooner we act to change our behaviors, the easier (and cheaper!) it will be to mitigate the effects of climate change.

Just to be clear, Hansen’s paper describes large scale glaciation occurring when CO2 fell to 425 +/- 75ppm.  The low end of that range?  350ppm.  Which we’ve already passed.  It can be argued that the long-term policy goal should be no more than 350ppm.  A radically different planet is in our future if we deviate from that level.

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2 thoughts on “Climate Change Information Update

  1. Weatherden writes:

    “In concert with the delayers’ misinterpretation of temperature data, they’re also saying that there is ‘record ice growth this winter’ in the Arctic. Of course, this has to mean global cooling, right? Not so much, actually. Remember that 2007 saw the greatest loss of Arctic sea ice in one year since measurements were recorded. Last year, over 2 million sq km of Northern Hemispheric Sea Ice disappeared. From that condition, it wouldn’t take much for record ice creation to occur, especially during a strong La Nina event. Indeed, that’s what the last portion of the graph shows. The largest message the graph shows is the long-term behavior of ice anomaly: further away from the mean in the negative direction.”

    The last six months have shown the greatest increase in Arctic sea ice recorded in the usual winter upswing. The peak sea ice extent in the Arctic this year was greater than it has been in the previous four years, during which the “great melting” took place.

    While you are correct that there has been a long term decrease in the yearly maximum Arctic sea ice extent, just the opposite is true of the Antarctic, as can be seen in this data from the National Center for Environmental Prediction/NOAA. Clearly, the Antarctic sea ice extent anomaly has been slowly, but continuously increasing during the entire 30 year satellite record. In fact, the greatest yearly maximum ever recorded for the Antarctic occurred during the most recent yearly cycle, and the third highest yearly minimum occurred just a few weeks ago, as can be seen here.

    A quick summary can be found here

    Thank you for the opportunity to comment.
    Tom

  2. The sea ice anomaly for the Antarctic did indeed reach a recorded maximum this year, which makes sense if a strong La Nina was present. The anomaly reached 2M sq km: in area. A critical difference between area and volume exists. As I wrote in this post, the volume of the Arctic ice is very low: a great deal of long-term ice disappeared during the last boreal summer. While the areal extent of Antarctic ice is anomalously high, these data do not demonstrate an increase in volume.

    If the Antarctic ice sheet is still in good health, all the better. It’s that sheet and the sheet over Greenland that should be very closely monitored since they are currently on land.

    Thanks for commenting.

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