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."

Comments

Interesting...

[Seoulstriker]

If this is the warmest in so many years, then back then it was hotter that what we have now.

Re:Interesting...

[Dashing Leech]

"a) it's not very probable we happen to be in the warm part of a cycle"

Not that I disagree with the overall belief that it is humans causing the warming trend, but your arguments are not valid. Pick any part of a cycle and you can say the same thing as above. Replace "warm" with "cold". If you believe the models we are on the way upward too, so it's not even a distinct point like a peak high or low. If the cycle is 1000 years of normal temps, 10 years of high temps, and 1000 years of normal temps, then I can see your argument (a 1/100 chance of being in the warm spot when we happen to figure out the cycle). But not something that could cycle over hundreds to thousands of years that we don't have sufficient data to get full cycles for. (Or even not a cycle, just a natural trend with or without us.)

The second argument (b) says nothing about the validity of a cycle argument. Newton's models of motion accurately portray what happens if I drop a hammar. That doesn't make them "right" and rule out other explanations such as relativity. (Fine, pick on the analogy, but the point is that 1 model working in some cases does not invalidate other possible models.)

I do think that we play a part in global climate change. But that's just a belief on enough circumstantial evidence. The data is not conclusive and no model (natural or human-caused) explains some of the major observations.

Cue the misunderstandings

[Anonymous Coward]

Let's take a pool on exactly how many posts this story will receive from partisans claiming that because the earth has been this warm in the past (the 800s) through natural causes, the earth either is not unusually warm now, or if it is warm now it must be because of natural causes--

not realizing that (1) the thing that makes manmade global climate change distinguishable from natural global climate fluctuations is not how warm the earth has become, but how quickly and consistently the earth has warmed since the industrial revolution;

and (2) the problem with manmade global climate change is not how warm the earth is now, but how warm it will become if this consistent, quick rise continues...

What's your guess? 10? 40? 100?

Snapshot

[AnonymousJackass]

The findings support the argument for global warming as a result of human interference rather than natural climate change.

No they don't. What about the Little Ice-Age? That was a major gloabl climate change that was certainly not induced by man.
Fact is, we're looking at a ~2000 year snapshot of an incredibly comlex system that's a few billion years old.
I'm not saying that there isn't claimte change -- of course there is. I'm also not saying that man doesn't affect it -- of course we do. But what I'm saying is that we don't know how we are affecting it. Maybe the "Little Ice-Age" ended because of man. Perhaps we saved ourselves from freezing to death by creating a cozy CO2 blanket?
My 2c...

Re:Snapshot

[lgw]

A stable climate is a myth. There's no evidence of such a thing.

It's true that human CO2 emissions are pushing climate change in some direction, but no one has a clue whther the results of that change will be more or less pleasant then the climate change that would have happene without human intervention.

So we don't know which way we're driving, all we know is we're driving quickly. That's reason for concern, to be sure, but not for despair.

Re:If only it felt like it

[OwnedByTwoCats]

And, in a few years, when melting arctic and Greenland ice has disrupted the Atlantic Conveyor, northern europe, including Great Britain and Scandanavia, will be much, much colder.

Re:Global warming is a myth because we say it is.

[pete-classic]

You said:

It's stating the facts, not going to extreme left positions and saying humans are causing the earth to heat up.

The article said:

The researchers think their work bolsters the case that global warming due to human activity has created a change in climate unlike anything seen in more than a millennium.

What the fuck?

-Peter

Re:If only it felt like it

[Daniel_Staal]

The warming of the globe as a whole will cause some locations to actually cool down, as air and water currents re-route.

This does not change the fact that the globe as a whole is warming.

(And frankly it is irrelevent whether humans are to blame or not. It is warming, which is going to cause climate change. Are we ready for it? If not, we may want to try to stop it (or at least slow it down).

I doubt we are.)

I feel like I'm taking Crazy Pills!

[jamesdps]

I'm going insane here -- everyone is saying "how does this prove anything if it was warmer in 800AD?" THAT'S NOT WHAT THE ARTICLE SAYS! "Warmest in 1200 years" does NOT implicitly mean it was warmer 1200 years ago, people -- read the article, we CAN ONLY TEST BACK 1200 years using ice cores, trees, etc.... it was COLDER 1200 years ago, that's what the article says... and as for the folks who mentioned the Little Ice Age, etc. -- yes, they mention that too (and the Medieval Warm Period from 890 to 1170), but both eras were not CONTINUOUSLY warm or cool, but were PUNCTUATED by hot and cold SPELLS... The concern of global warming is that the CONTINUOUS temperature is changing. I will concede that without data before 800AD, the study is looking at a pretty small sample of time, and that there are so many factors in such a hugely complex weather system to take into consideration, so I have no problem at all with those arguments, just with the fact that the majority of people here seem to be good at quickly sorting through text looking for keywords (such as "since 800AD") without actually COMPREHENDING what they are reading.... /rant.

Re:Food for thought

[Anonymous Coward]

Yet, in spite of all this, the climate is still cooler than it was in 800 AD.

No, TFA doesn't say this at all. Rather, their reconstruction only goes back to 800 AD; apparently they felt like the quality of their data wasn't sufficient to support a hemispheric temperature reconstruction prior to this -- not too surprising if they're relying heavily upon tree rings, though others (e.g. Mann et al.) have taken this sort of reconstruction back at least 2000 years (with essentially the same results).

Re:If only it felt like it

[spun]

That's an important point. Calling the phenomenon Global Warming is perhaps misleading. Some places will get warmer, others colder. Some will be wetter, some dryer. Dumping more energy into a chaotic system like the climate means more extreme climates, not necessarily warmer ones.

Implications

[Peter Mork]

Not necessarily:

Assume we are looking at n time intervals numbered 1, 2, ..., n. If the maximum observed temperature was in interval n, we can assert that this interval was the warmest of the last n intervals.

Now consider interval 0. If this interval is warmer than n, the strongest assertion we can make is that the recent interval is the warmest of the last n. If the recent interval is warmer than 0, we could make a stronger assertion. However, the validity of 'warmest of the last n remains.

In effect, you are assuming that the researchers made the strongest possible assertion. Another alternative is that they were only able to measure a certain number of intervals.

Re:Global warming is a myth because we say it is.

[greginnj]

Now what doesn't amke sense to me is that they say "yes, it has been this warm (and warmer) before.... BUT this somehow proves that it's human activity making it warm this time."

Huh? Where in TFA do they say that it's been that warm (and warmer) before? They say:

the 20th century has been the most widespread and longest period of unusual climate experienced at any time during at least the past 1,200 years

Note well the 'at least', meaning they only looked at tree rings going back that far; it doesn't show that anything was necessarily warmer (or colder). This study has no info on pre-800AD.

Now let's look at the other hot-button sentence:

The researchers think their work bolsters the case that global warming due to human activity has created a change in climate unlike anything seen in more than a millennium.

The key word here is 'bolsters', not 'makes' the case. How could it bolster? Because we know CO2 is going up, and climate models show CO2 leads to heating. Also note that there are two things to prove -- first, is global warming occurring (whatever the cause), and second, what caused it? This study makes a strong case for proving the first. The fact that the tree-ring data agrees with the CO2 models must be explained somehow -- it could be a coincidence, it could be there are errors with the models or with the tree-ring study, or it could be CO2 heating. I'd accept your criticism if they said 'conclusively proves', but 'bolsters' is acceptable.