Climate 'warmest for millennium'

[zippyjuan]

Last Updated: Friday, 10 February 2006, 04:23 GMT From the BBC

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Climate 'warmest for millennium'
By Paul Rincon
BBC News science reporter



The last 100 years is more striking than either the Medieval Warm Period or Little Ice Age

Timothy Osborn, UEA
In the late 20th Century, the northern hemisphere experienced its most widespread warmth for 1,200 years, according to the journal Science.

The findings support evidence pointing to unprecedented recent warming of the climate linked to greenhouse emissions.

University of East Anglia researchers measured changes in fossil shells, tree rings, ice cores and other past temperature records or "proxies".

They also looked at people's diaries from the last 750 years.

Timothy Osborn and Keith Briffa of UEA analysed instrument measurements of temperature from 1856 onwards to establish the geographic extent of recent warming.

Then they compared this data with evidence dating back as far as AD 800.

The analysis confirmed periods of significant warmth in the Northern Hemisphere from AD 890 - 1170 (the so-called "Medieval Warm Period") and for much colder periods from 1580 - 1850 (the "Little Ice Age").

Natural records

The UEA team showed that the present warm period is the most widespread temperature anomaly of any kind since the ninth century.

"The last 100 years is more striking than either [the Medieval Warm Period or Little Ice Age]. It is a period of widespread warmth affecting nearly all the records that we analysed from the same time," co-author Timothy Osborn told the BBC.

Osborn and Briffa used 14 sets of temperature records from different locations across the Northern Hemisphere.

The records included long life evergreen trees growing in Scandinavia, Siberia and the Rockies which had been cored to reveal the patterns of wide and narrow tree rings over time. Wider rings related to warmer temperatures.

The chemical composition of ice from cores drilled in the Greenland ice sheets revealed which years were warmer than others.

Dear diary

The researchers used proxy data developed from the diaries of people living in the Netherlands and Belgium during the past 750 years that revealed, for example, the years when the canals froze.

"These records extend over many centuries and even thousands of years. We simply counted how many of those records indicated that, in any one year, temperatures were warmer than average for the region they came from," said Dr Osborn.

Professor John Waterhouse, director of the Environmental Sciences Research Centre Anglia Ruskin University in Cambridge commented: "Although we're getting increasingly accurate measurements of present-day temperature, we've got nothing like that from the past to compare those with.

"There's much uncertainty in past reconstructions. You've got to look at the reconstructed data in the past in light of the likely errors that those data have."

But he added: "As we get more and more evidence in, it is looking as if the current period is the warmest for over 1,000 years."

In November, Science published a paper showing atmospheric levels of the greenhouse gases carbon dioxide and methane are higher now than at any time in the past 650,000 years.

[LegendKiller]

All I gotta say is Hockeystick. It's been discredited. Vostok cores also sholw that in the long-run, we are in a period of high temps which fluctuate and then come down off cyclical highs.

I do not really believe in global warming, all long-run analysis discredit it.

[verve247]

On a side note, there is a prediction of another little ice age hitting the world sometime this mid century.

[zippyjuan]

All I gotta say is Hockeystick. It's been discredited. Vostok cores also sholw that in the long-run, we are in a period of high temps which fluctuate and then come down off cyclical highs.

I do not really believe in global warming, all long-run analysis discredit it.

You are correct that the Vostok Cores show that temperatures have varied in the past. They also have shown a corelation between wamer periods and higher concentrations of greenhouse gasses such as methane and carbon dioxide. http://www.daviesand.com/Choices/Pre...ning/New_Data/ The second page shows more recent trends. http://www.daviesand.com/Choices/Pre...ook/index.html
If we are producing more of these gasses we may be increasing the amount of warming that occurs (even if it is part of a natural cycle) and dramatically effect the climate. Just a few degrees shift in average temperatures can have a major effect on the planet. This effects rainfall and what crops can be grown where. I would prefer to err on the side of caution and try to reduce such emissions if possible. Levels of carbon dioxide are higher now than at any time measured in the cores.

[welfareloser]

well, hey, this should get interesting... evangelical christians decided to re-interpret their religion and suddenly put their stamp of approval on environmentalism, so now it's okay for republicans to stop pretending that we don't need to worry about all that nature crap. i guess bush's next flip-flop will be on the existence of global warming if he wants to please his base ...

[LegendKiller]

You are correct that the Vostok Cores show that temperatures have varied in the past. They also have shown a corelation between wamer periods and higher concentrations of greenhouse gasses such as methane and carbon dioxide. http://www.daviesand.com/Choices/Pre...ning/New_Data/ The second page shows more recent trends. http://www.daviesand.com/Choices/Pre...ook/index.html
If we are producing more of these gasses we may be increasing the amount of warming that occurs (even if it is part of a natural cycle) and dramatically effect the climate. Just a few degrees shift in average temperatures can have a major effect on the planet. This effects rainfall and what crops can be grown where. I would prefer to err on the side of caution and try to reduce such emissions if possible. Levels of carbon dioxide are higher now than at any time measured in the cores.

So, let me ask you, when the NFC wins the Super Bowl does that mean the stock market will go down?

We do not know enough about long-term trends and our effects on them to say with 100% certainty that we *AREN'T* drawing a spurrious corellation.

Sure, we are in the highest point now, but the previous highest point wasn't the last highest point. Does that mean that 325,000 years ago cavemen discovered fire and that caused more greenhouse cases to be released?

One wave in the ocean isn't the as another. One economic cycle isn't the same as the previous, or even the previous 50. Standard deviation of even things we *think* we know well, such as econmics, is very high. The corellation coefficient is very low since the overall data suggests that human intervention has not caused previous deviations from the mean.

Using science and statistical fact, global warming cannot be proven. The data set is too small, the peak is too high, and the effects cannot be conclusively made.

[Grimm]

Using science and statistical fact, global warming cannot be proven. The data set is too small, the peak is too high, and the effects cannot be conclusively made.

True. But one camp, the enviornmentalists, want to be cautious about the suspected causes and research the issue.
The other camp wants to just deny it and NOT do any research.

It's a legitimate question. Are the emisions produced by our society haveing an effect on global weather?
We should find out the answer.

[zippyjuan]

We do not know for certain what may have caused the past increases to CO2 and other gasses. We do know that man is presently producing more than he has at any time in the past (mostly in the last 100 years) so this added to the natural cycles of CO2 could greatly increase the impact of the natural ones. The previous peaks have been within a range and in fact the peaks had been declining until the last 100 years- the period of man's great increase in the burning of fuels- and we are presently over two times higher than the historical range for the high points or even the highest in the past. Man is definately having an effect on CO2 and other gasses. You are right that we do not know the full impact that may have on the environment, but as I said, I prefer to err on the side of trying to control them before it is too late (if it is not already). In a couple thousand years we will know if we caused any problems, but by then it will be too late to do anything about them since they would have already happened.

[InfiniteNothing]

I've argued this too recently. All I have to say is trust the engineers or you'll have more challenger type explosions but on a global scale.
Link

[Markel]

All I gotta say is Hockeystick. It's been discredited. Vostok cores also sholw that in the long-run, we are in a period of high temps which fluctuate and then come down off cyclical highs.

I do not really believe in global warming, all long-run analysis discredit it.

Wow! Did you become a conservative all of a sudden?

[InfiniteNothing]

He's always been a conservative. He's just not the "patriotic" kind.

[LegendKiller]

He's always been a conservative. He's just not the "patriotic" kind.

Depends on what you term a conservative. I wouldn't besmirch my name with being called what passes for a conservative these days.

We do not know for certain what may have caused the past increases to CO2 and other gasses. We do know that man is presently producing more than he has at any time in the past (mostly in the last 100 years) so this added to the natural cycles of CO2 could greatly increase the impact of the natural ones. The previous peaks have been within a range and in fact the peaks had been declining until the last 100 years- the period of man's great increase in the burning of fuels- and we are presently over two times higher than the historical range for the high points or even the highest in the past. Man is definately having an effect on CO2 and other gasses. You are right that we do not know the full impact that may have on the environment, but as I said, I prefer to err on the side of trying to control them before it is too late (if it is not already). In a couple thousand years we will know if we caused any problems, but by then it will be too late to do anything about them since they would have already happened.

We know that we have high CO2 and high temps, but we do not know if that will last. Furthermore, being at the natural peak according to the Vostok cores, it could easily mean that we are high because it's just a high peak n the cycle.

There are many things about the planet we do not know. We don't fully understand why the vostok cores show such extreme temp/co2 measurements in such a nice cyclical pattern. Furthermore, we don't know whether it's us or just the planet reaching a natural or unatural high.

If you look here, you notice that we entered into a peak ~12,000 years ago and have stayed high. Are you saying that humans have caused the peak for 12,000 years? Or is 100 years or even 200 years indicative of a abnormal peak in over 12,000 years of peak data? How come we haven't cause a higher peak when in fact we have a significant deviation from the peak mean? One could extrapolate that we, through human intervention, have kept a high level inside that peak. However, if you look at the previous cyclical peaks, they have become more ragged and stay higher longer. How could we draw a perfect conclusion that humans = global warming when we are only applying 100 years, 1/12 of the current peak, of data?

http://en.wikipedia.org/wiki/Image:V...core-petit.png


Another question that should be asked is if there was such a strong correlation between Co2 and heat, then why hasn't heat spiked like Co2? Every other cycle it has been better correlated.


I am by no means saying we shouldn't reduce greenhouse gas emissions. However, I do not think that this is a huge sky falling scenario like many people would have you believe. Interesting article here...

http://news.ft.com/cms/s/fc181144-99...0779e2340.html

[zippyjuan]

The second article (we can only read one paragraph) is talking about natural CO2. Man is producing much more than is being absorbed by the planet. One article I saw (don't have a link right now) said that man produces 150 times more CO2 than natural sources. Even for the last 12,000 years, changes in temperature have tended to move in the same direction as CO2 levels. What caused the CO2 levels 12,000 years ago we do not know for sure. We do know what is causing higher levels now. It is only in the last 100 or so years that we broke through the normal levels of CO2 so we may be just now beginning to see some effects. The mechanisms are not completely understood and neither are if there is a delay factor as chemical, thermal or other reactions take time to make their way through the ecosystem. More CO2 this year may not mean a hotter year next year. Based on historical trends we should be near a high point in temperatures. There is no question that deserts have been growing and glaciers and icecaps melting more than in our recent history. Areas once in perma frost are starting to thaw. Ice at the North Pole is half the thickness it was thirty years ago.

[Houdini]

The second article (we can only read one paragraph) is talking about natural CO2. Man is producing much more than is being absorbed by the planet. One article I saw (don't have a link right now) said that man produces 150 times more CO2 than natural sources. Even for the last 12,000 years, changes in temperature have tended to move in the same direction as CO2 levels. What caused the CO2 levels 12,000 years ago we do not know for sure. We do know what is causing higher levels now. It is only in the last 100 or so years that we broke through the normal levels of CO2 so we may be just now beginning to see some effects. The mechanisms are not completely understood and neither are if there is a delay factor as chemical, thermal or other reactions take time to make their way through the ecosystem. More CO2 this year may not mean a hotter year next year. Based on historical trends we should be near a high point in temperatures. There is no question that deserts have been growing and glaciers and icecaps melting more than in our recent history. Areas once in perma frost are starting to thaw. Ice at the North Pole is half the thickness it was thirty years ago.

None of which proves man was the cause. It's sort of like the Ozone hole. Yes, it exists for a month or so each year, but we only saw it after we started looking at stratospheric ozone from satellites. A new finding doesn't mean a new occurrence. For all we know, the hole could be opening/closing/growing/shrinking every 2-200000 years. People were way too quick to put blame on humans' use of CFCs, etc., as the cause, simply because it was a new finding.

If deserts are getting hotter and permafrost areas are thawing, that doesn't necessarily mean that you or I had anything to do with it. We don't know the natural cycles of the planet, as we're just becoming sophisticated enough to measure them. At any rate, what are you doing, or what can I do to change things immediately? Typing on this computer and driving my car to work both pollute, as they both use some sort of fossil fuel, though in LA it's mostly nuclear on the grid.

[LPMiller]

yeah, but that seems a little see no evil, hear no evil. We may not have proof that some of this stuff doesn't happen naturally, which I agree with. But we also have plenty of pointers telling us yes, CFC's break down ozone, or that our own polution causes rises in CO2. Of course we affect the global environment. While how much is debatable, you cannot say we don't have any affect at all, and we should still do our part to not make things worse.

[Markel]

yeah, but that seems a little see no evil, hear no evil. We may not have proof that some of this stuff doesn't happen naturally, which I agree with. But we also have plenty of pointers telling us yes, CFC's break down ozone, or that our own polution causes rises in CO2. Of course we affect the global environment. While how much is debatable, you cannot say we don't have any affect at all, and we should still do our part to not make things worse.

I agree that we need to be careful. However, there are many that seem to think that the sky is falling.

[Houdini]

I'm mostly with the two stupids above, however I still maintain that the science just isn't there. I've been to some damn interesting lectures from those without agendas who have presented credible facts, and while I agree that our impact on the environment in that way is feasable, it's minimal at best.

[LPMiller]

there is no one without an agenda.