June 22, 2006 4:23 PM PDT

Earth's temperature at 400-year high

It hasn't been this hot at least since the Spanish Armada, according to the National Research Council.

Measurements from tree rings, boreholes and retreating glaciers provide sufficient evidence that the surface temperature of the Earth in the last few decades of the 20th century was higher than any comparable period for the past 400 years, according to a report released Thursday by the NRC that both reinforces and curtails conclusions in an earlier study.

The data also indicates that many parts of the Earth in the past 25 years were hotter than anywhere else on the globe than any other 25-year period since 900 A.D.

The cause? A lot of it is from human activity. "Surface temperature reconstructions for periods before the Industrial Revolution--when levels of atmospheric greenhouse gases were much lower--are only one of multiple lines of evidence supporting the conclusion that current warming is occurring in response to human activities, and they are not the primary evidence," stated a press release that accompanied the study.

The report was requested by Congress after a controversy arose last year over surface temperature reconstructions published by climatologist Michael Mann and his colleagues in the late 1990s. Mann concluded that the warming of the Northern Hemisphere in the last decades of the 20th century was unprecedented in the past thousand years. The 1990s, Mann added, was the warmest decade ever and 1998 was the warmest year ever.

The researchers behind the new report said they had "high confidence" in the conclusion that global temperatures were at a peak over the last 400 years. However, because of the spotty nature of data earlier, particularly for the Southern Hemisphere, it had less confidence in Mann's conclusions for the period from 900 to 1600 and "very little confidence" in conclusions about previous years. As a result, the researchers had little confidence in the conclusion that the previous decade was the hottest ever and 1998 was the hottest year.

Still, the researchers found Mann's conclusion that temperatures in the Northern Hemisphere in the last few decades represented a high for the last 1,000 years to be plausible. None of the climate reconstructions in the new study indicate that temperatures were warmer during medieval times than during the past few decades. (The Spanish Armada took place in 1588.)

Scientists do not have temperature records going back hundreds of years. Temperature records actually go back only 150 years. To determine surface temperature, researchers examine corals, ocean and lake sediments, ice cores, cave deposits and documentary sources such as historic drawings of glaciers.

Climactically speaking, the last 400 years have been sort of a roller coaster ride. From 1500 to 1850, the Earth was wrapped in what climatologists call the little ice age, where temperatures dipped. Since 1850, they have been rising. This last period also coincides with the Industrial Revolution.

In the past century, the temperature of the Earth has risen about 1 degree Farenheit. Scientists, however, believe the rate of temperature increase will accelerate. Ice reflects sunlight, so as glaciers retreat, more heat gets absorbed by the Earth. The greenhouse gas layer will also grow from burning fossil fuels, thereby trapping more heat.

It doesn't sound like much, but relatively small fluctuations like that can have a significant impact over a wide surface. A 5 degree to 8 degree rise in global temperature in the next 100 years, expected by many scientists, could cause sea levels to rise half a meter and put some island nations underwater.

"Six to 10 degrees is the difference between the temperature today and the temperature of the deepest ice age," Steve Chu, director of Lawrence Livermore Labs, said recently.

See more CNET content tagged:
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45 comments

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And in 900 A.D.?
Was the warm Earth at that time caused by Rollo the Viking's
flatulence?
Posted by nicmart (1829 comments )
Reply Link Flag
yep!
must have been. my question is where the hell were the thermometers to tell us this back then? i think it is a lot of guess work.!?
Posted by startawar (3 comments )
Link Flag
And in 900 A.D.?
Was the warm Earth at that time caused by Rollo the Viking's
flatulence?
Posted by nicmart (1829 comments )
Reply Link Flag
yep!
must have been. my question is where the hell were the thermometers to tell us this back then? i think it is a lot of guess work.!?
Posted by startawar (3 comments )
Link Flag
The Earth Will Shake Us Off Like Fleas
I've heard so many people concerned that we're destroying the planet. Ha! The arrogance! As if the human race can destroy a planet. The earth will get rid of off us long before we'll do any significant damage. And that, of course, is the problem.
Posted by mrvista (22 comments )
Reply Link Flag
The Earth Will Shake Us Off Like Fleas
I've heard so many people concerned that we're destroying the planet. Ha! The arrogance! As if the human race can destroy a planet. The earth will get rid of off us long before we'll do any significant damage. And that, of course, is the problem.
Posted by mrvista (22 comments )
Reply Link Flag
Well, this proves it!
Yep, this proves it, once and for all. If only we hadn't burned all those fossil fuels in our cars 400 years ago, we wouldn't be in the mess we're in today! I hear the original inventors of cars wanted to use hamster power, and use twisted rubber bands for airplanes.

If only we'd listened!
Posted by Joe Bolt (62 comments )
Reply Link Flag
Well, this proves it!
Yep, this proves it, once and for all. If only we hadn't burned all those fossil fuels in our cars 400 years ago, we wouldn't be in the mess we're in today! I hear the original inventors of cars wanted to use hamster power, and use twisted rubber bands for airplanes.

If only we'd listened!
Posted by Joe Bolt (62 comments )
Reply Link Flag
Lunacy
So we've recorded the highest temperatures in 400 years? So
what! We've also got a planet that's over 4 BILLION years old, and
scientific evidence showing that we've gone through warming
and cooling cycles that FAR EXCEED what we're now going
through.
Unfortunately, what we have in the press, is the "Science of
Politics" instead of pure science.
Want to have some fun? Locate a copy of the show "Ocean
Mysteries: Fury in the Abyss". Core samples taken from the ice
caps show that the earth has been through MASSIVE shifts in
temperature, MILLIONS of years before white guys in SUV's
populated the 'burbs with their BBQ pits.
UGH!
Posted by GGGlen (491 comments )
Reply Link Flag
Lunacy indeed
The only lunatics are the ones in denial like yourself. While measuring the highest temperature in the last 400 years may not be enough proof to you that we are having an adverse affect on the planet, the fact remains that these record breaking temperatures are destroying ecosystems close to the equator and putting millions of people and animals in danger of dying horrible slow deaths from lack of food and water.

According to you we're not at a critical point of climate change so tell me, what evidence do you need to be convinced. Larger storms, decimated lands that once used to be green and fertile, entire island chains sinking under water, floods in Manhattan? Because whatever evidence you need, is on it's way! Unfortunately by the time we'll convince people like you, it's going to be too late to do anything about it.

I'm no environmentalist but your defence of calling these findings "science of politics" is an insult. If you're digusted with reading science in the news, pick up an article published in a respected scientific journal. You'll find that scientists overwhelmingly agree that climate change is a fact.
Posted by slickmachines (18 comments )
Link Flag
Hello, I have been looking for a copy of Ocean Mysteries: Fury in the Abyss for almost 10 years now, and have never found one. Do you know where I could get a copy of this? Thanks, Mike
Posted by mikentOMFA (1 comment )
Link Flag
Lunacy
So we've recorded the highest temperatures in 400 years? So
what! We've also got a planet that's over 4 BILLION years old, and
scientific evidence showing that we've gone through warming
and cooling cycles that FAR EXCEED what we're now going
through.
Unfortunately, what we have in the press, is the "Science of
Politics" instead of pure science.
Want to have some fun? Locate a copy of the show "Ocean
Mysteries: Fury in the Abyss". Core samples taken from the ice
caps show that the earth has been through MASSIVE shifts in
temperature, MILLIONS of years before white guys in SUV's
populated the 'burbs with their BBQ pits.
UGH!
Posted by GGGlen (491 comments )
Reply Link Flag
Lunacy indeed
The only lunatics are the ones in denial like yourself. While measuring the highest temperature in the last 400 years may not be enough proof to you that we are having an adverse affect on the planet, the fact remains that these record breaking temperatures are destroying ecosystems close to the equator and putting millions of people and animals in danger of dying horrible slow deaths from lack of food and water.

According to you we're not at a critical point of climate change so tell me, what evidence do you need to be convinced. Larger storms, decimated lands that once used to be green and fertile, entire island chains sinking under water, floods in Manhattan? Because whatever evidence you need, is on it's way! Unfortunately by the time we'll convince people like you, it's going to be too late to do anything about it.

I'm no environmentalist but your defence of calling these findings "science of politics" is an insult. If you're digusted with reading science in the news, pick up an article published in a respected scientific journal. You'll find that scientists overwhelmingly agree that climate change is a fact.
Posted by slickmachines (18 comments )
Link Flag
A better article
A majority of scientists may believe that global warming is a
problem, but a majority of scientists don't work in the
climatology field.

"While many are highly skilled researchers, they generally do not
have special knowledge about the causes of global climate
change," explains former University of Winnipeg climatology
professor Dr. Tim Ball. "They usually can tell us only about the
effects of changes in the local environment where they conduct
their studies."

This is highly valuable knowledge, but doesn't make them
climate change cause experts, only climate impact experts.

So we have a smaller fraction.

But it becomes smaller still. Among experts who actually
examine the causes of change on a global scale, many
concentrate their research on designing and enhancing
computer models of hypothetical futures. "These models have
been consistently wrong in all their scenarios," asserts Ball.
"Since modelers concede computer outputs are not "predictions"
but are in fact merely scenarios, they are negligent in letting
policy-makers and the public think they are actually making
forecasts."

Appearing before the Commons Committee on Environment and
Sustainable Development last year, Carleton University
paleoclimatologist Professor Tim Patterson testified, "There is no
meaningful correlation between CO2 levels and Earth's
temperature over this [geologic] time frame. In fact, when CO2
levels were over ten times higher than they are now, about 450
million years ago, the planet was in the depths of the absolute
coldest period in the last half billion years." Patterson asked the
committee, "On the basis of this evidence, how could anyone
still believe that the recent relatively small increase in CO2 levels
would be the major cause of the past century's modest
warming?"

Patterson concluded his testimony by explaining what his
research and "hundreds of other studies" reveal: on all time
scales, there is very good correlation between Earth's
temperature and natural celestial phenomena such changes in
the brightness of the Sun.

<a class="jive-link-external" href="http://www.canadafreepress.com/2006/harris061206.htm" target="_newWindow">http://www.canadafreepress.com/2006/harris061206.htm</a>
Posted by sbwinn (216 comments )
Reply Link Flag
A better article
A majority of scientists may believe that global warming is a
problem, but a majority of scientists don't work in the
climatology field.

"While many are highly skilled researchers, they generally do not
have special knowledge about the causes of global climate
change," explains former University of Winnipeg climatology
professor Dr. Tim Ball. "They usually can tell us only about the
effects of changes in the local environment where they conduct
their studies."

This is highly valuable knowledge, but doesn't make them
climate change cause experts, only climate impact experts.

So we have a smaller fraction.

But it becomes smaller still. Among experts who actually
examine the causes of change on a global scale, many
concentrate their research on designing and enhancing
computer models of hypothetical futures. "These models have
been consistently wrong in all their scenarios," asserts Ball.
"Since modelers concede computer outputs are not "predictions"
but are in fact merely scenarios, they are negligent in letting
policy-makers and the public think they are actually making
forecasts."

Appearing before the Commons Committee on Environment and
Sustainable Development last year, Carleton University
paleoclimatologist Professor Tim Patterson testified, "There is no
meaningful correlation between CO2 levels and Earth's
temperature over this [geologic] time frame. In fact, when CO2
levels were over ten times higher than they are now, about 450
million years ago, the planet was in the depths of the absolute
coldest period in the last half billion years." Patterson asked the
committee, "On the basis of this evidence, how could anyone
still believe that the recent relatively small increase in CO2 levels
would be the major cause of the past century's modest
warming?"

Patterson concluded his testimony by explaining what his
research and "hundreds of other studies" reveal: on all time
scales, there is very good correlation between Earth's
temperature and natural celestial phenomena such changes in
the brightness of the Sun.

<a class="jive-link-external" href="http://www.canadafreepress.com/2006/harris061206.htm" target="_newWindow">http://www.canadafreepress.com/2006/harris061206.htm</a>
Posted by sbwinn (216 comments )
Reply Link Flag
you missed the part about tree rings and sciency stuff huh
My may have missed the early mention of measuring tree rings and other such sciency stuff. Plant growth follows a recognised pattern. Yes, it's true, they can use old wood to tell things from the past.
Posted by jabbotts (492 comments )
Reply Link Flag
Math=hard?
"The past" as you've so eloquently posted (all of 400 years),
equates to .0000001% of the Earth's past, and I'm being extremely
generous, considering a 4 billion year old guess as to it's birth.
Posted by GGGlen (491 comments )
Link Flag
you missed the part about tree rings and sciency stuff huh
My may have missed the early mention of measuring tree rings and other such sciency stuff. Plant growth follows a recognised pattern. Yes, it's true, they can use old wood to tell things from the past.
Posted by jabbotts (492 comments )
Reply Link Flag
Math=hard?
"The past" as you've so eloquently posted (all of 400 years),
equates to .0000001% of the Earth's past, and I'm being extremely
generous, considering a 4 billion year old guess as to it's birth.
Posted by GGGlen (491 comments )
Link Flag
Could have been a believer!
Could have been a believer! Gore turned the issure into a political issure by the way he entended to solve the problem with Kyoto. Now it would take a hundred thousand to convince me of anything but.

I will wait till someone I can trust steps forward. Not these self appointed savers of humanity. I tend to go with the other "nay sayers".
Posted by ronaldlclark (4 comments )
Reply Link Flag
Could have been a believer!
Could have been a believer! Gore turned the issure into a political issure by the way he entended to solve the problem with Kyoto. Now it would take a hundred thousand to convince me of anything but.

I will wait till someone I can trust steps forward. Not these self appointed savers of humanity. I tend to go with the other "nay sayers".
Posted by ronaldlclark (4 comments )
Reply Link Flag
I would hope that we are warmer...
Considering that for 250 of those 400 years we were in the Little Ice Age (the one that killed the Vikings in Greenland, changed agriculture in Europe, was indirectly responsible for the potato famine in Ireland), I would hope we are warmer than then.

To end the LIA, temperatures started rising. They seem to have continued rising. Are current temperatures due to man, cattle, the earth, or a mixture of the above. Did our friendly researchers factor out all abnormal cooling and heating events (Krakatoa, releases of methane hydrates and other events that 19th/20th century science didn't know about) before they published their research?
Posted by bndavis (5 comments )
Reply Link Flag
I would hope that we are warmer...
Considering that for 250 of those 400 years we were in the Little Ice Age (the one that killed the Vikings in Greenland, changed agriculture in Europe, was indirectly responsible for the potato famine in Ireland), I would hope we are warmer than then.

To end the LIA, temperatures started rising. They seem to have continued rising. Are current temperatures due to man, cattle, the earth, or a mixture of the above. Did our friendly researchers factor out all abnormal cooling and heating events (Krakatoa, releases of methane hydrates and other events that 19th/20th century science didn't know about) before they published their research?
Posted by bndavis (5 comments )
Reply Link Flag
Nice!
I see that replies are being excluded from the discussion.
Oh well, they might as well simply delete the thread and pretend it
never happened
;)
Posted by GGGlen (491 comments )
Reply Link Flag
Nice!
I see that replies are being excluded from the discussion.
Oh well, they might as well simply delete the thread and pretend it
never happened
;)
Posted by GGGlen (491 comments )
Reply Link Flag
Maybe a technical glitch?
:)

Once more, with feeling;
"According to you we're not at a critical point of climate change"?
According to me? Not hardly. According to CO2 samples drawn
from both ice sheets, north and south, which conclusively prove
that the earth not only goes through warming and cooling
cycles, but has gone through MASSIVE changes, millions of years
before **** Sapiens appeared on the scene.
For example, ever hear of Michigan? It's a state in the US that
claims, as one of its most distinguishing features, being
surrounded by the largest bodies of fresh water on the planet.
Care to hazard a guess how these lakes were formed?
Well, according to the science of geology, the Great Lakes were
carved out when MILE HIGH glaciers retreated from the North
American continent. Mile high glaciers don't disappear
overnight, it takes thousands of years of global warming to
reduce them, and at that time, the glaciers reached the Equator.
What you're mis-representing, is the idea that "people like
me" (a typical over-generalazation heaped upon those who don't
"think what they're told to, and when to), disagree with the fact
that the earth is warming.
WELL DUH, it is!!! As is Mars, according to such an unscientific
body as NASA.
The fact remains that global warming (and global cooling)
happen naturally. Are we contributing to the warming effect?
You bet! But when all good science points to the fact that the
earth is overdue for an ice age (Geology has shown that they
occur every 30,000 to 60,000 years or so), I consider it a
benefit.
See? While you might whine about "millions of people and
animals in danger of dying horrible slow deaths", Ice ages result
in a near total mass extinction. Fossil records clearly show that
99.99% of every species that has ever existed on earth are now
gone, so get over it, it's nature. The Earth changes, whether you
like it or not,
Oh, and for you science newbies? The Earth's magnetic field has
been in decline since we've 1st begun measuring such stuff.
I can't WAIT to hear the spin on that story, since fossil records
have shown that it's a phenomena that's been happening for 4
billion years!
Global warming will PALE in comparison to the damage done
when the magnetic field dies and reverses (as it has done
numerous times in the past) and the Earth is, once again,
exposed to massive amounts of solar radiation.
Posted by GGGlen (491 comments )
Reply Link Flag
Maybe a technical glitch?
:)

Once more, with feeling;
"According to you we're not at a critical point of climate change"?
According to me? Not hardly. According to CO2 samples drawn
from both ice sheets, north and south, which conclusively prove
that the earth not only goes through warming and cooling
cycles, but has gone through MASSIVE changes, millions of years
before **** Sapiens appeared on the scene.
For example, ever hear of Michigan? It's a state in the US that
claims, as one of its most distinguishing features, being
surrounded by the largest bodies of fresh water on the planet.
Care to hazard a guess how these lakes were formed?
Well, according to the science of geology, the Great Lakes were
carved out when MILE HIGH glaciers retreated from the North
American continent. Mile high glaciers don't disappear
overnight, it takes thousands of years of global warming to
reduce them, and at that time, the glaciers reached the Equator.
What you're mis-representing, is the idea that "people like
me" (a typical over-generalazation heaped upon those who don't
"think what they're told to, and when to), disagree with the fact
that the earth is warming.
WELL DUH, it is!!! As is Mars, according to such an unscientific
body as NASA.
The fact remains that global warming (and global cooling)
happen naturally. Are we contributing to the warming effect?
You bet! But when all good science points to the fact that the
earth is overdue for an ice age (Geology has shown that they
occur every 30,000 to 60,000 years or so), I consider it a
benefit.
See? While you might whine about "millions of people and
animals in danger of dying horrible slow deaths", Ice ages result
in a near total mass extinction. Fossil records clearly show that
99.99% of every species that has ever existed on earth are now
gone, so get over it, it's nature. The Earth changes, whether you
like it or not,
Oh, and for you science newbies? The Earth's magnetic field has
been in decline since we've 1st begun measuring such stuff.
I can't WAIT to hear the spin on that story, since fossil records
have shown that it's a phenomena that's been happening for 4
billion years!
Global warming will PALE in comparison to the damage done
when the magnetic field dies and reverses (as it has done
numerous times in the past) and the Earth is, once again,
exposed to massive amounts of solar radiation.
Posted by GGGlen (491 comments )
Reply Link Flag
Recent research...
conclusions suggest that post-ice age warming may have occurred in 10s to 100s of years, not thousands. The most recent poster in this discussion could greatly benefit from a post-grad course in quaternary geology. There is just enough data in the post to suggest greater knowledge of the field. However, to those who've read and discussed the most recent scholarly research and publications, it is clear that the data in the post is improperly interpreted and not presented with a depth of understanding of the field.

Though ice cores and other research data do suggest the cycle of warming/cooling has happened frequently over the earth's lifetime, no one creature on the caused the warming, until now. This will wreak havoc on the earth's population of all creatures. It will have a great impact on our ability to feed ourselves, it will likely create millions of refugees, and will make the weather much more unpredictable. And we've only done it to ourselves. That's the horror and the tragedy.
Posted by coconinoite (27 comments )
Reply Link Flag
Recent research...
conclusions suggest that post-ice age warming may have occurred in 10s to 100s of years, not thousands. The most recent poster in this discussion could greatly benefit from a post-grad course in quaternary geology. There is just enough data in the post to suggest greater knowledge of the field. However, to those who've read and discussed the most recent scholarly research and publications, it is clear that the data in the post is improperly interpreted and not presented with a depth of understanding of the field.

Though ice cores and other research data do suggest the cycle of warming/cooling has happened frequently over the earth's lifetime, no one creature on the caused the warming, until now. This will wreak havoc on the earth's population of all creatures. It will have a great impact on our ability to feed ourselves, it will likely create millions of refugees, and will make the weather much more unpredictable. And we've only done it to ourselves. That's the horror and the tragedy.
Posted by coconinoite (27 comments )
Reply Link Flag
Think Of Frogs
This isn't a blog it is a Frog. Censored to opinions of the editor!
Posted by ronaldlclark (4 comments )
Reply Link Flag
Think Of Frogs
This isn't a blog it is a Frog. Censored to opinions of the editor!
Posted by ronaldlclark (4 comments )
Reply Link Flag
Global Warming not a myth
Granted, the earth is warming. Of this there is no disputation. The question is, is it our fault? Carbon dioxide is not the only activity that can cause warming, as patterson point out, "when CO2 levels were over ten times higher than they are now, about 450 million years ago, the planet was in the depths of the absolute coldest period in the last half billion years."
Posted by entropy4139 (2 comments )
Reply Link Flag
Exactly. Yes global warming is occurring. The question is how much are we contributing to this problem? 400 years ago it was this hot. What man made issue cause this 400 years ago? If it was not man made was this a climate cycle? 450 mil years ago with co2 levels rising there was a global cooling is a great point. This is now become a political issue and because of this the science has become politically partisan on both sides. We may never come to a true answer because of all the politics involved .
Posted by ocpud299 (2 comments )
Link Flag
 

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