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20th Century Warmest In 1200 Years
gcranston writes "Research from the University of East Anglia in Norwich, U.K. shows that the 20th century was the warmest for the northern hemisphere since approximately 800AD. Historical climate data were calculated from weather 'proxies' such as tree rings, ice cores, and seashells from Europe, Asia, and North America, and attempted to address the shortcomings of earlier studies. The findings support the argument for global warming as a result of human interference rather than natural climate change."
The article doesn't say what happened in the 8th century, just that tree rings don't reliably go back any farther. They must be using only specific species of trees, though, because there there are several species of living trees that are much, much older. Do their rings not reflect temperature, too?
The article contains almost no technical data, but it does say there have been been conflicting results:
"In 2003, a team led by researchers from the Harvard-Smithsonian Center for Astrophysics announced that it believed the 20th century wasn't the warmest, nor the one with the most extreme weather of the past 1,000 years.
"But this research has been criticized for its selection of the indicators used to estimate historic temperatures, among other problems."
The article doesn't say what indicators the Harvard-Smithsonian group used, just that they think their indicators are better.
I'd be willing to guess (although I won't be around long enough to find out) that we're just in some sort of cycle ... it's warm now ... but in a few hundred thousand years or so we'll be back to another ice age again!
Good guess. We're in the middle of an ice age right now (ice ages last a long time). We're in a brief worm period between long cold periods. The Vostock ice core data shows a cycle that's about 100 k years long. Based on the limited data we have (only 4 cycles), we should have begun a rapid return to normal conditions for this ice age about 10 k years ago. It's not clear why we haven't.
The thing is, no one really understands what drives that 100 k year cycle - does CO2 gradually accumulate until some threshhold is reached, which kicks of some powerful feedback mechanism? Is it all about Solar activity levels? Why didn't it start getting cold again 10 k years ago?
We understand the feedback mechanism involved in the longer (100 M year or longer) cycle between ice ages and a tropical Earth. The weathering of rock removes CO2 from the air, and the more of the land are that is covered by glaciers, the less this happens. That cycle is huge and powerful, but slow: it's pretty unlikely we happen to be alive at the end of the current ice age.
Socialism: a lie told by totalitarians and believed by fools.
Earth is way overdue for a magnetic field reversal. They have an average interval of 1/4 million years and it has been 3/4 million already since the last one. Some say it is beginning with the loss of a magnetic pole in certain places in the southern hemisphere. It could be the cause of the ozone layer loss because as the field weakens it radius at the poles grows. When the field is strong the field meets at the poles in a tight radius.
Here are some cool sims from Los Alamos National Laboratory.
As we lose protection more radiation gets through and mother earth gets a temperature. I'm not saying that 100 years of intense burning hasn't contributed but this seems to be an ignored fact that may be contributing in a large manner.
I first heard of this from watching a NOVA program. Here is the NOVA site on earths magnetic fields with some animations.
Ok, now where did I put the SPF 10,000?
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The problem here, fundamentally, is too many science-types go to unending lengths using bad science and bad use of statistics to prove themselves right. This conversation constantly degenrates into two uninformed groups of people spouting completely false nonsense at each other based entirely on a misuse of statistics. Even in this slashdot thread you will see people getting modded up for citing (incorrectly) correlative evidence as causitive evidence.
The fundamental issue here is correlation. Good climatologists are at war with correlation implying causality. They are unable to produce proper control experiments, so no matter how convincing their results, it's able to be dismissed by others. No good science should look at correlative evidence (as you have stated plenty) and draw conclusions. Guess what, since 1980, Jupiter has seen a HUGE increase in the number of comet strikes of the previous decades. But we can't pin that on global warming.
The fundamental question is how much has humanity effected the global warming of this planet. Just showing that it is warming is completely and totally irrelevant. The important scientific question, and the one most difficult to answer, is how much humans have contributed. The methods whereby CO2 heats up a planet are fairly well understood, and no one with a sane state of mind can deny that humanity has made things worse. The scientific debate remains to what degree. Slashdot karma-whores can continually abuse the general lack of statistical know-how by stating "look how much warmer it is now!" and get modded up. The fact of the matter is using the metric of "difference in temperature in time" is completely and utterly meaningless in a debate about humanity's contribution to global warming.
And we don't even need to get into the ridiciously horrible statistical fallacies possible when one begins using "extremes" and "records" as a basis for drawing conclusions.
So here we are again, another long rant from two sides of an argument where those arguing are not in possesion of most of the facts.
It always amazes me that these two sides will get into bitter feuds over this subject and no one seems to want to put it in any context. For me what it comes down to is this: we can spend a lot of money, time, and research trying to find out if we are a contributing factor to global warming, only to discover it may be too late, or we can spend even more money, time, and research trying to change the way we interact with the atmosphere. And in the end if those who claim that global warming is impacted by humans are right and we listened to them then we are on our way to fixing it and have a cleaner environment for the future. If they are wrong and we listened to them we still have a cleaner environment and we might just find that all those chemicals we were pumping into the atmosphere had other effects which would then be limited. If, on the other hand we don't listen to them and they are right then we have to learn to live in a new world climate and deal with the vast ammounts of crap we have been pumping into the atmosphere for centuries.
What it comes down to, for me, is this: do we want to risk the global climate on this? Is it worth the piece of mind to know that what happens is out of our control instead of our fault?
Let's tackle this one by one.
'Antartic climate cooling and terrestrial ecosystem response' Nature 415: 517-20
"Side-looking radar measurements show West Antartic ice is increasing at 26.8 gigatons/yr. Reversing the melting trend of the last 6000 years"
This is predicted by climate change models. The cause is precipitation - increase in ocean temperature puts moisture into the air, which comes down as snow at the central regions of the poles. Meanwhile, the edges of the polar ice masses melt.
"Both satellite data and ground stations show slight cooling over the last 20 years."
Is that from 1996? Post 1999, it emerged that the satellite data were making systematic errors. After correcting those errors, the measurements now support GW. As for ground, see above.
"During the last four interglacials, going back 420,000 years, the Earth was warmer than it is today."
"Less Antartic ice has melted today than occured furing the last interglacial"
But the onset of those temperatures was much, much slower than now. That's why global warming is so alarming. We're going to get the added temperature from the interglacials on top of the unrelated human caused changes,
The Sahara has shrunk since 1980
Title - plants reclaim the desert. Why? Perhaps the plants are better adapted to desert enivironments. Perhaps global warming has increased local humidity. Sahara expansion is more complicated than just a matter of global warming effects.
Note that *none* of the above have concluded that global warming is contradicted. They just sound like they contradict global warming, when what is happening is precisely what one would expect.