Another AGU stunner: Evidence that Antarctica has warmed significantly over past 50 years

Posted on

"Another AGU stunner: Evidence that Antarctica has warmed significantly over past 50 years"

hot-penguin.jpgScientists know the Antarctic ice sheet is losing mass “100 years ahead of schedule” (see “AGU 2008: Two trillion tons of land ice lost since 2003” and “Antarctic ice sheet hits the fan“).

Now, as Nature‘s climate blog reports, two studies presented last week at the AGU meeting document what should not be a surprise, but still is. New research suggests “the entire Antarctic continent may have warmed significantly over the past 50 years“:

The study, led by Eric Steig of the University of Washington in Seattle and soon to be published in Nature, calls into question existing lines of evidence that show the region has mostly cooled over the past half-century.

they found warming over the entire Antarctic continent for the period 1957-2006. Restricting their analysis to 1969 to 2000, a period for which other studies have found a net cooling trend, Steig’s study found slight cooling in east Antarctica, but net warming over west Antarctica.

How did they perform the analysis of the harshest, most remote climate on the planet?

Steig and colleagues combined satellite thermal infra-red collected over 25 years with weather station data for the region. Although the satellite data span a shorter time period and are accurate only for blue sky days i.e. when there is no cloud cover, they provide high spatial coverage of the region, which cannot be obtained from discrete ground measurements. In contrast, the weather station data provide complete temporal resolution over the past half-century….

They independently confirmed these trends by using data from automatic weather stations, and excluding the satellite data.

Turns out they were not the only study to present at the AGU meeting to find that warming extends beyond the Antarctic’s Peninsula region. David Bromwich of the Byrd Polar Research Centre at Ohio State also presented at AGU his new study, “Surface and Mid-tropospheric Climate Change in Antarctica,” which found:

Near-surface air temperatures and 500-hPa temperatures over Antarctica for 1960-2007 have been reconstructed over the entire continent using manned station observations and radiosonde records, respectively, from the READER database maintained by British Antarctic Survey. The 50-year trends found in our near-surface temperature reconstruction agree with recent work by others using a variety of spatial extrapolation techniques. It is found that the statistically significant Antarctic Peninsula near-surface warming on an annual basis has spread into West Antarctica reaching as far as east as the Pine Island Bay-Thwaites Glacier region.

The warming is most marked in recent years with 2007 being the warmest year in the 1960- 2007 interval…. The warming over West Antarctica is maximized in the spring (SON) and in that season statistically significant warming stretches across all of West Antarctica and into northern Victoria Land. Weak near- surface warming is found over East Antarctica and the continent as a whole on an annual basis although continental warming in the spring is statistically significant and driven largely by the strong and widespread changes in West Antarctica.

How credible and comprehensive is this research? It is based on a three-year study funded by the National Science Foundation’s Office of Polar Programs (Glaciology), in which Bromwich worked with the U.S. National Center for Atmospheric Research and the British Antarctic Survey. As Bromwich explains on his website, he blended model data and observations “to reconstruct a record of Antarctic near-surface temperature back to 1960″:

Considering that there are only 15 long-term observational records of near-surface temperature over the entire continent of Antarctica (1-1/2 times the size of the U.S.), this record fills important gaps in our current knowledge of the spatial and temporal variability of Antarctic near-surface temperatures. Only two other such observational records – that depict temperatures over the entire continent – exist. We have collaborated with the creators of the other two datasets … to perform the most comprehensive evaluation of Antarctic near-surface temperatures yet….

The key finding is that temperatures over most of Antarctica have been warming subtly since the early 1990s, consistent with a leveling-off of trends in the Southern Hemisphere Annular Mode over the same period. This result contrasts with most recent results indicating the temperatures over Antarctica (other than on the Antarctic Peninsula) haven’t changed much in recent decades.

So notwithstanding the amateur meteorologist-deniers who sometimes comment on this blog and elsewhere about how cold it is outside right now, the whole damn planet is warming and melting.

“The science is beyond dispute… Delay is no longer an option. Denial is no longer an acceptable response”

Related Posts:


« »

11 Responses to Another AGU stunner: Evidence that Antarctica has warmed significantly over past 50 years

  1. mauri pelto says:

    Bromwich is the person to trust on this. I taught a course on Antarctic Climate glacier interactions at the University of Maine in 1987 and his work was the best then for the continent and still is when it comes to winds and temperature.

  2. Johnny Rook says:

    Meanwhile at the other pole, have you seen the trend line for sea-ice refreezing at NSIDC recently? After hovering well above last years refreeze rate for several months it has now crossed below last year’s refreeze line, which puts it even farther below the 1979-2000 average.

    Last year we had lots of thin 1st year ice, which is why there was so much summer ice melt even though temperatures were cooler. If this current trend continues were going to have lots of thin 1st and 2nd year ice but less ice refreezing overall. And then if we get an El Niño come spring…

    2008 Arctic Sea-Ice Refreeze Trend Line Dropping Below Last Year’s

    Blogging for the future at Climaticide Chronicles

  3. Copied your post to my blog. Hope you don’t mind.

  4. Mark Shapiro says:

    Is anyone looking at the salinity of the Arctic and Antarctic Oceans?

    Those two trillion tons of land ice lost since 2003 have mean fresh water going into the oceans, lowering the salinity and raising the freezing point. Thus you would expect the sea ice to freeze earlier in the autumn and thaw later in the spring. We don’t see that.

    In other words, lower salinity might actually be temporarily masking a larger catastrophe at the poles.

    Does this “hold water”?

  5. Sure they look at salinity, see for example,

    Tons of references there.

  6. Mark Shapiro says:

    Thanks Tenney – there it is:

    ” . . . on centennial to millennial time scales Antarctic Ice Sheet (AIS) can melt and moderate warming in the Southern Hemisphere, by up to 10°C regionally, in a 4 × CO2 scenario. This behaviour stems from the formation of a cold halocline in the Southern Ocean, which limits sea-ice cover retreat under global warming and increases surface albedo, reducing local surface warming. . . .”

    from “Antarctic ice-sheet melting provides negative feedbacks on future climate warming” in GRL 2008, by Swingedouw and others.

    So land ice melts, freshens the sea water, slows sea-ice retreat, reduces albedo, cools the air (a little) locally. This masks AGW. Holy cow.

  7. Brian says:

    So, the idea is to use models to basically fill in the data, since the data isn’t there. Then, based on “modeled” data, there is supposed to be warming.

    Even though this same author previously noted in another publication that he authored that there were statistically insignificant trends either way.

    Can I model my bank account so that there is more money in it, and then claim that reality needs to match my model?

    Why not stick with the actual data? Either the trend is there or it isn’t. I don’t need to artificially “compute” what the data “should” be.

    [JR: I love you deniers. First off, you have cited a paper that was submitted in 2002! There has been a want of data and improved analysis since then. Second, all analysis of long-term trends is done with the help of computers. What are you some sort of a Luddite? If you want to accuse scientists of fraud, as you do in the third paragraph, why don’t you? The reason that fraud, especially fraud that persists for an extended period of time, is still rare in science compared to pretty much every other field is that the results must meet the review process, and then they are published for all to see, and challenge. If you want to slander the good name of climate scientists, you probably belong on another web site.]

  8. Brian says:

    So a paper submitted in 2002 is such a long way off. And apparently, we knew nothing about numerical methods or data analysis before that point.

    Furthermore, it’s not “slander” to cite someone’s words back at them. Bromwich said, a mere six years ago, that the literature showed that there was no statistically significant trend (either up or down) in the temperature data. I note that you don’t deny that he said that. How could you, I provided the link.

    You need to read the abstract. The “data” is “reconstructed.” In other words, he took the actual data (which he previously stated showed no statistically significant trend up or down), and then used a computer program which attempted to fill in more data. So it is very accurate to say that he created data, and based his statements on the created data. Not surprisingly I suppose, he finds a warming trend in the “model data.”

    But only six years prior, he acknowledged that the literature was conflicting. From the article I cited … “In recent years, scientists have discovered surprising, and occasionally conflicting, climate changes taking place in the Antarctic. Jones (1995) finds an average warming at the surface over all of Antarctica (especially the Antarctic Peninsula) by analyzing station data from 1957 to 1994. Comiso (2000) notes a cooling trend between 1979 and 1998 from infrared Advanced Very High Resolution Radiometer (AVHRR) imagery and from station records, but the trends are not statistically significant for either dataset.”

    So some researchers found warming, others cooling, and “the trends are not statistically significant for either dataset.”

    I’m merely pointing out that the research goes both ways apparently, depending on the data. And that there was no statistical significance in the up or down trend. In other words, you could make no real judgment about the trend from a statistical standpoint. That is what Bromich (who you linked to in the OP) stated.

  9. Joe says:


    Did you even read the new study — or my post?

    Bromwich has now combined three different data sets in his new study. And he used a new analytical technique he recently refined for his snowfall work.

    And, yes, the OLD study you linked to only went through 1999. We’ve had another decade of data since then — and while you deniers may not accept the fact, this last decade has been by far of the warmest in the 150 year temperature record.

    So it is absurd to write, “the research goes both ways apparently, depending on the data.” The research goes one way as the planet heats up and we get more data — and we get smarter about how to analyze it.

    Bromwich appears to be a real pioneer in this specific area of figuring out the temperature in Antarctica. So it is no surprise that his techniques are improving over the years.

    Finally, data is reconstructed in much if not most of all scientific research. We gather photons from telescopes so essentially all of our extra-solar-system science is “reconstructed.” Same for particle physics. Same for medicine actually. What do you think CT and MRI scans are? They don’t actually go inside your brain, you know.

    What is especially funny about your critique is that of all the recent temperature datasets in climate science, the ones that are the most “reconstructed” — and hence, according to you, the least trustworthy — are the satellite data. Satellites don’t measure temperature directly at all. And they take their data through a column of the atmosphere.

    If you want to start rejecting constructed temperature data sets, start by ignoring all of the satellite data. Indeed, if we have left that analysis up to Christy and Spencer — who had screwed up the reconstruction for years (all their mistakes mysteriously in the same direction) — we would still be left with the denier meme that the satellite data doesn’t show warming. Fortunately, the scientific method triumphs in the end.

  10. Brian says:

    The gathering of photons is the data itself. The scanning of your brain is an indirect method of gathering data. It is not “making up” what is going on in your head.

    However, you need to be honest, filling in the “interstices” and gaps in data using some sort of estimation algorithm is, in essence, creating data.

    Granted, there is actual data mixed in with the “model data” … but even I can take a set of data showing a slight cooling trend (or warming trend, it doesn’t matter) and fill in the gaps in the data to reverse the trend.

    Again, you don’t deny that Bromwich said that the literature showed statistically insignificant cooling and warming trends, depending on the dataset used.

    [JR: Final paragraph deleted since I’m tired of links to denier sites.

    Yes, I do “deny” what you wrote, as my previous comment explained. He has more datasets now PLUS more recent data now PLUS a better analytical technique.

    Your first paragraph above suggests to me you have no idea what you are talking about. Either data is “reconstructed” or it isn’t. Anytime you aren’t physically measuring something directly, you are reconstructing data. It ain’t a big deal here.]

  11. Brian says:

    So, you delete that portion of the post clearly showing that NOAA took weather station data which showed a downward trend in temp, and after they “homogenized” the data, it now showed an upward trend.

    I wonder … if the oil or coal companies took data, and “adjusted” it to show something other than what the raw data said … you’d be all over that.

    It is one thing to make a correction for a known calibration or measurement problem.

    But filling in “interstices” means filing in the gaps in the data. In that case, you are clearly estimating what you think the data should be in that gap. That is data *creation.*

    Data “reconstruction” (as used in climate modeling), is likewise data creation. Be honest. Nobody knows what the actual temperature was, but you might come up with an estimate based on certain proxies. But as is being demonstrated on the “denier” sites that you profess to abhor, these “reconstructions” have problems as well.

    And you question whether I know what I’m talking about … well, I do have a degree in mechanical engineering and a law degree … so I think I have a better grasp of math and statistics than the average person might.

    [JR: I deleted a post to a denier website. I have also blogged why the NASA and Hadley temp records likely underestimate actually warming. I’m glad people are out there pointing out insignificant points for the real scientists to factor in or not depending on whether they are real or bogus.
    I just think it is irrelevant stuff. Pretty much every place on the planet that could be melting is.