There was a Medieval Warm Period (900-1100 AD), in central Greenland at any rate. But we knew that — that’s when the Vikings were naming it Greenland, after all.
*the axis is degrees C. The Greenland ones are actual (yep, it’s cold there), the Vostok are delta of current temp
* CO2 can migrate in ice, but all that does is smooth out the CO2 record. But CO2 is not the temperature proxy — it’s the isotopic fractions of 18Oxygen and deuterium in the actual ice itself.
United Kingdom’s Met (Meteorological) Office announced that the 2000-2009 decade “has been, by far, the warmest decade on the instrumental record”, and that 2009 is on track to become the fifth warmest year in the past 160 years, continuing the warming trend that has accelerated since the 1970s
We’re pretty lucky to be here during this rare, warm period in climate history. But the broader lesson is, climate doesn’t stand still. It doesn’t even stand stay on the relatively constrained range of the last 10,000 years for more than about 10,000 years at a time.
Does this mean that CO2 isn’t a greenhouse gas? No.
Does it mean that it isn’t warming? No.
Does it mean that we shouldn’t develop clean, efficient technology that gets its energy elsewhere than burning fossil fuels? Of course not. We should do all those things for many reasons — but there’s plenty of time to do them the right way, by developing nanotech. (There’s plenty of money, too, but it’s all going to climate science at the moment. ) And that will be a very good thing to have done if we do fall back into an ice age, believe me.
For climate science it means that the Hockey Team climatologists’ insistence that human-emitted CO2 is the only thing that could account for the recent warming trend is probably poppycock.
If we want climate stability then we will the need the geoengineering and climate control technology to achieve that result.
There is a rundown from a climate skeptic who indicates why the historical numbers matter and why the slope of warming matters and why the amount of effect from CO2 matters and why accurate models matter and why the current models do not appear to be accurate.
1. The slope of recent temperature increases is used as evidence for the anthropogenic theory.
The more the warming falls into a documented natural range of temperature variation, the harder it is to portray it as requiring man-made forcings to explain. This is also the exact same reason alarmist scientists work so hard to eliminate the Medieval Warm Period and little ice age from the temperature record. Again, the goal is to show that natural variation is in a very narrow range, and deviations from this narrow range must therefore be man-made.
2. It is already really hard to justify the huge sensitivities in alarmist forecasts based on past warming — if past warming is lower, forecasts look even more absurd.
When projected back to pre-industrial CO2 levels, these future forecasts imply that we should have seen 2,3,4 or more degrees of warming over the last century, and even the flawed surface temperature records we are discussing with a number of upwards biases and questionable adjustments only shows about 0.6C.
Sure, there are some time delay issues, probably 10-15 years, as well as some potential anthropogenic cooling from aerosols, but none of this closes these tremendous gaps. Even with an exaggerated temperature history, only the no feedback 1C per century case is really validated by history. And, if one assumes the actual warming is less than 0.6C, and only a part of that is from anthropogenic CO2, then the actual warming forecast justified is one of negative feedback, showing less than 1C per century warming from manmade CO2 — which is EXACTLY the case that most skeptics make.