These charts and studies, summarized at RealClimate.org, illustrate how rapidly global temperatures are warming: faster than ever, and they've actually tried to account for the possibility that maybe at some point in the past there was a similar spike and then a quick reduction, but they've found that it couldn't have gone unnoticed in the scientific data. So, we're #1!!! The conclusion is that by 2100 temperatures will be ~3° C (*not* Fahrenheit) higher than now, meaning melting ice, rising seas, bigger storms, and a new geological epoch. I suggest calling it the Inhofene epoch, after Sen. James Inhofe (R-Hellmouth), who insists that climate change is a big old hoax cooked up by scientific researchers because of their well-known bias favoring higher numbers in all things.

From the article:

The important point is that the rapid rise in the 20th Century is unique throughout the Holocene. Whether this really is true has been intensively discussed in the blogs after the publication of the Marcott paper. Because the proxy data have only a coarse time resolution – would they have shown it if there had been a similarly rapid warming earlier in the Holocene?

I think for three reasons it is extremely likely that there was not such a rapid warming before:

1. There are a number of high-resolution proxy data series over the Holocene, none of which suggest that there was a previous warming spike as strong as in the 20th Century. Had there been such a global warming before, it would very likely have registered clearly in some of these data series, even if it didn’t show up in the averaged Marcott curve.

2. Grant Foster performed the test and hid some “20th C style” heating spikes in earlier parts of the proxy data to see whether they are revealed by the method of Marcott et al – the answer is a resounding yes, they would show up (albeit attenuated) in the averaged curve, see his article if you are interested in the details.

3. Such heating must have a physical basis, and it would have to have quickly disappeared again (would it have lasted, it would be even more evident in the proxy data). There is no evidence in the forcing data that such a climate forcing could have suddenly appeared and disappeared, and I cannot imagine what could have been the mechanism. (A CO2-induced warming would persist until the CO2 concentration decays again over thousands of years – and of course we have good data on the concentration of CO2 and other greenhouse gases for the whole Holocene.)

and...

This May, for the first time in at least a million years, the concentration of carbon dioxide in our atmosphere has exceeded the threshold of 400 ppm. If we do not stop this trend very soon, we will not recognize our Earth by the end of this century.