Wednesday, August 8, 2012

Paper finds Medieval Warm Period in Arctic was much warmer than the present

A paper published in Polar Research finds that temperatures at two sites in the Arctic were much warmer than at the end of the 20th century. At one site, Longyearbyen, the11-year running-mean peak winter temperature was a remarkable 9C warmer than at the end of the record in 2000. At the 2nd site, Vardo, the11-year running-mean peak winter temperature was about 3.3C warmer than at the end of the record in 2000. As the NIPCC Report explains,

Not only is there nothing unusual, unnatural or unprecedented about the most recent surface air temperatures at Longyearbyen and Vardo, it is pretty clear that it was significantly warmer at both locations during the peak warmth of the Medieval Warm Period, when there was way less CO2 in the atmosphere than there is today. And this observation suggests - as do many others from all around the world - that anthropogenic CO2 emissions are not the great threat to humanity and the biosphere that climate alarmists claim them to be, for something in the environment appears to be effectively counteracting whatever "greenhouse effect" they may produce.

In introducing the purpose for their study, Divine et al. (2011) write that "the recent rapid climate and environmental changes in the Arctic, for instance, sea-ice retreat (e.g., Comiso et al., 2008) and ice-sheet melting (e.g., van den Broeke et al., 2009), require a focus on long-term variability in this area in order to view these recent changes in the long-term context," which is truly essential if one desires to know just how unusual, unnatural or unprecedented the recent warming of the Arctic has been.

Working with ice cores extracted from Svalbard at Lomonosovfonna in 1997 (Isaksson et al., 2001) and at Holtedahlfonna in 2005 (Sjorgren et al., 2007), Divine et al. used the δ18O data derived from them to reconstruct 1200-year winter (Dec-Jan-Feb) surface air temperature histories for nearby Longyearbyen (78.25°N, 15.47°E) and farther-afield Vardo (70.54°N, 30.61°E, in northern Norway), by calibrating (scaling) the δ18O data to corresponding historically-observed temperatures at the two locations, which for Longyearbyen were first collected in 1911 and for Vardo have been extended back to 1840 as a result of the work of Polyakov et al. (2003).

The winter surface air temperature reconstructions, which are depicted in the figure below, begin at the peak warmth of the Medieval Warm Period at approximately AD 800, and they decline fairly steadily to the coldest period of the Little Ice Age at approximately AD 1830, after which they rise into the 1930s, decline, and then rise again, to terminate just slightly lower than their 1930s' peaks near the end of the 1990s.

As may readily be determined from Divine et al.'s results, the 11-year running-mean peak winter temperature of the Medieval Warm Period was approximately 9°C greater than the end-of-record 11-year running-mean peak winter temperature at Longyearbyen, while it was about 3.3°C warmer at Vardo.

Not only is there nothing unusual, unnatural or unprecedented about the most recent surface air temperatures at Longyearbyen and Vardo, it is pretty clear that it was significantly warmer at both locations during the peak warmth of the Medieval Warm Period, when there was way less CO2 in the atmosphere than there is today. And this observation suggests - as do many others from all around the world - that anthropogenic CO2 emissions are not the great threat to humanity and the biosphere that climate alarmists claim them to be, for something in the environment appears to be effectively counteracting whatever "greenhouse effect" they may produce.