The last few decades were the warmest on Earth in the past 400 years, and may well have been warmer than any comparable period since the Middle Ages, U.S. scientists reported on Thursday.

In a new report by the National Research Council, researchers said they were highly confident the mean global surface temperature was higher in the past 25 years than any comparable period during the previous four centuries.

They had less confidence the past quarter-century was hotter than any comparable period in the years from 900 to 1600, but found that plausible. For the years before 900, the scientists said they had very little confidence about what the Earth’s mean surface temperatures were.

The scientists also noted that temperature reconstructions for periods before the Industrial Revolution — when levels of climate-warming greenhouse gases were much lower — supported the notion the current global climate change was caused by human activities, rather than natural variations in climate.

Nothing unexpected in this report; but, I thought I’d post it because it explains how some of this research is formulated. There are folks who wonder how anything could be known before the weather guy started showing up on TV.

Figuring out global temperatures over the past 150 years is relatively simple, since reliable records exist. But for the years and centuries before that, researchers must read clues left by the growth rings on trees, the retreat of glaciers and even old paintings and diaries that document climate.

Such clues are called proxies, and scientists began using them in sophisticated ways in the 1990s to estimate Earth’s surface temperature in past eras.

The council’s report was prompted by a request from the U.S. Congress, spurred by a controversial 1998 report in the journal Nature that used a number of sources, including proxies, to estimate temperatures in the Northern Hemisphere over the last 1,000 years.

One would hope the folks in Congress who made the request — read the report.



  1. Frank IBC says:

    So we’re still cooler than we were in the Middle Ages.

  2. Aaron says:

    The paradox here is that if we stop using fossil fuels the earth will heat up faster!

    http://www.pbs.org/wgbh/nova/preview/i_3310.html

    Yikes!

  3. Max Bell says:

    I remember making a trip to the dump when it was just a landfill, rather than a transfer station, and listening to the guy in the truck next to me rant about how stupid it was to be dumping the stuff on land when there was so much space in the ocean. Besides just being a hazard to marine life, I couldn’t fathom that anyone would think anything like that would be a good idea, but as far ahead as he saw it, it was just unused space.

    Now, besides hard-core depletion of fish stocks through over fishing, we’ve got whole sections of the coast line that are simply dead because there’s no oxygen at lower levels, problems with algae blooms killing off everything near them because of the sewage being pumped into the water and lovely little anomalies like islands of styrofoam forming in ocean crosscurrents.

    Not too long ago, my dad had the bright idea to buy one of those steel shipping containers to provide storage and workspace so that he could continue repairing harleys after he closed shop and retired.

    Mention of this prompted an interesting tirade about how frequently these containers apparently simply fall off ships — in theory they’re designed to float, but if you’re out sailing, as he’s been doing a lot lately, you discover that they submerge just enough so that if you get right on top of one, you can see that it’s there. According to what he told me, its not an isolated problem, but an increasingly serious hazard for small boaters.

    This report struck me because it went out on a limb to say explicitly that the temperature increase was the product of human activity. I guess that’s progress considering not too long ago Reagan was telling us that trees caused more pollution than cars and Dixie Lee Ray could claim that CO2 emissions were the product of termite mounds. Something that’s distinctly noticable around here is that for the past couple of decades, the temperature in the Seattle-Tacoma area is always at least one degree warmer than anywhere else in the state. If you’ve ever spent any time driving here, that probably doesn’t have any shock value.

    Regardless of where the ultimate truth lies, however, if there is any catastrophic consequence of any of this, the best case scenario is that the pace of change does not exceed the pace of human reason.

    Given that we’re getting pretty close to killing off every species in the family that makes up the great apes, it seems like a pretty foregone conclusion that we’ll render ourselves similarly extinct eventually.

  4. moss says:

    Take a refresher course in reading English, Frank.

    Better yet, read the links.

  5. mike cannali says:

    At 2pm today the temperature had increased 20 degrees in just 12 hours. Certainly by dark it will be up another 10 degrees and soon all life will disappear on the planet.

  6. James Hill says:

    No wonder my tan looks so good!

  7. ab cd says:

    The global warming fearmongers are spinning this like crazy. What it really means is that the so called hockey-stick graph should be thrown out. They were not able to recreate it, and just don’t know about things older than 400 years ago. The media spinners are changing words like ‘possibly’ into ‘likely’.

  8. ef gh says:

    The global warming fearmongers are spinning this like crazy. What it really means is that the so called hockey-stick graph should be thrown out. They were not able to recreate it, and just don’t know about things older than 400 years ago. The media spinners are changing words like ‘possibly’ into ‘likely’.

    PS why have I been blacklisted?

  9. Pmitchell says:

    If it was as hot as it is now 400 years ago then how are we in global warming ? There were less than 750 million humans on earth and they could not have released any where near they supposed toxic gasses that are now supposedly causing global warming, but the temp was the same as now

    I say that is a real big mark against ole GORE and his doom and gloom side show.It shows that the temp changes are natural and not man made

    we just need a big volcanic eruption to help cool things off again it has been over 10 years since the earth has had a decent eruption to blow ash and debris into the upper atmosphere to cool things off a degree or so

  10. Uncle Dave says:

    AB CD, our new spam filter inexplicably marked you as spam. I OKed one of your comments on another post and emailed John about checking into it.

  11. Eideard says:

    Dave, AB CD — I figured out how to reverse it when someone gets snared. Still not certain why it happens, though.

    AB CD — I’ve seen a couple instances where the spam filter gets uptight over browsers not having Java enabled. You might check your browser for updates.

  12. iscott says:

    I seem to remember hearing something about the possibility of a mini ice age that lasted until the early 1900s . That would explain the rising temperatures over the last 100 years or so.

  13. mike cannali says:

    Funny how global warming seems to get it’s most PR when the Dems are trying to elect someone.

  14. moss says:

    If you saw that PBS program, Aaron, it was premised that removing the pollution from the fossil fuels might accelerate global warming. Another wonderful reason to leave the sleazy bastards alone — who are in charge — NOT.

    Though, I would never be surprised to hear that used as a campaign “talking point”.

  15. Todd Henkel says:

    I certainly do not consider myself an environmentalist, but I do appreciate clean air and not living next to a toxic waste dump. And I would really like to use renewable energy versus continual support of the oil industry and nations.

    But the following statement makes me cringe…

    …researchers said they were highly confident…

    The only thing I am confident in is that they want more research dollars. Can’t say I blame them as they need to earn a living, but what is the point of such research. This one involves “proxy” leaps of faith rather than hard science.

    What needs to start showing up is more research that maps how to move away from fossil fuel dependency. Looks like it will require a combination of bio-fuels, solar, wind and nuclear. So why wait? Start legislation to begin implementing now rather than later!!! Entire economies must be shifted so let’s not wait to do so in a crisis mode!!!

  16. James Hill says:

    Todd, I agree with your statements. To go further, the smug nature in which these stories are spun make them less likley to get picked up by the public at large.

  17. Douglas A Griffiths says:

    Ok, if man if responsible for global warming then what caused the last seven or so warming and cooling cycles over the past many thousands (millions?) of years? Back in those times man was not present or for you supposed scientific types pre-man was just dragging his knuckles. Many weather scientists believe that this old earth naturally goes through many hot and cold cycles. They also understand that climatic changes are very much influenced by the temperature of the sun, i.e., check out the sun spot cycles well known for hundreds of years now.

    Now for you liberals I believe I have just the next theory for you. Could daylight savings time be the actual cause of global warming? Just think about it, the extra hour of sunlight each day would cause a slight warming every day. Right? Is it a coinsidence that about the time daylight savings time became law that global warming just happened to start? No way. So let’s all get together to repeal daylight savings time! Go liberals.

  18. Greg Mc says:

    All of this was an interesting plot line in the novel State of Fear, (Michael Crichton’s latest?). The book itself was fiction and a little waek at that, but if you look through the references and sources, there’s a ton of good data available. If you haven’t read it, I highly recommend it. Good fodder for both sides.

  19. traaxx says:

    Since it warmed up to bring us out of the Ice Age, should we be trying to go back to an Ice Age? What caused the Earth to warm up then? Even if the US and Europe both completly stop the use of cars, and anything else the produces a “greenhouse gas”, both India and China have said they will not stop. I really doubt that South America will either. For all the savings in the production of green house gases we may strive to obtain all it will take to wipe out a decade of these efforts is one volcano eruption, ie Krakatoa. Were already due for several now, according to scientists.

  20. Peter says:

    It’s funny reading the comments on here from people trying to stick their heads in the sand. There are very few climate scientists who do not accept the fact that human activities have caused atmospheric changes that are influencing the earth’s energy balance. Yes, the atmosphere is an extremely complicated system, but the evidence of recent warming is irrefutable, and the link to human activity is too clear to be merely co-incidence. It’s not only the degree of warming, but the pace of change that is troubling. People, however, always believe what they want to believe.

    I wonder, just what sort of evidence would it take to convince the naysayers?

  21. ab cd says:

    It’s colder now than 1998. So recently we’ve in a cooling trend. What evidence will convince people. How about models that actually hold up? They keep changing the numbers for predicted warming because things are just too complicated. The scientists are not anywhere near as unanimous as the media claims. Read through those UN reports, and try looking at the scientist reports and not the general summaries written by activists.

  22. George of the city says:

    I wonder just what sort of evidence it will take to convince the doomsayers they are wrong. Either way you really can’t control it. but I find all the hot air being dispenced about it amusing


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