Earth’s Climate Shows 2,000-Year Cooling Trend

People who swallow global warming alarmism almost never know anything about the Earth’s climatic history. Next time one of your friends or relatives starts giving you the global warming routine, ask him or her to graph the temperature history of the last 500,000 years. Or 20,000 years. Or 2,000. Trust me: the supposed climate expert won’t be able to do it. Yet putting the modest temperature increase of the latter half of the 20th century into historical context is the first prerequisite of any intelligent evaluation.

From Watts Up With That? comes a report on a new tree-ring study that covers the last 2,000 years. Are tree-ring analyses valid? I don’t know, but the alarmists use them all the time, and they are certainly more reliable over a relatively reasonable time frame like 2,000 years. The study finds that global temperatures have been gradually declining over that time:

In a paper published in the Journal of Quaternary Science, Esper et al. (2014) write that tree-ring chronologies of maximum latewood density (MXD) “are most suitable to reconstruct annually resolved summer temperature variations of the late Holocene.”

The late Holocene is the geologic era in which we are living.

As the international team of researchers from the Czech Republic, Finland, Germany, Greece, Sweden and Switzerland describes it, this history depicts “a long-term cooling trend of -0.30°C per 1,000 years over the Common Era in northern Europe” (see figure below). Most important of all, however, they note that their temperature reconstruction “has centennial-scale variations superimposed on this trend,” which indicate that “conditions during Medieval and Roman times were probably warmer than in the late 20th century,” when the previously-rising post-Little Ice Age mean global air temperature hit a ceiling of sorts above which it has yet to penetrate.

This graph shows the long-term cooling trend as well as the relatively wide variations on smaller time scales. Click to enlarge:

esperetal2014b

This finding is consistent with other studies indicating that the Earth is currently cooler than it has been about 90% of the time since the end of the last Ice Age. So, could it get warmer? Yes, and with any luck, it will.

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