Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 248

Arctic Temperature Change and Arctic Ampliication
What temperature changes have been seen in the Arctic? Proxy temperature data from lake
sediments, tree rings and ice cores show that for 2,000 years prior to about 1800, the Arctic
was slowly cooling. This is a trend that is consistent with knowledge on how Earth's cli-
mate has responded in the past to the state of the sun's energy output (luminosity) and to
Earth's orbital characteristics. However, since 1800, the temperature record reveals a warm-
ing trend, with Arctic summer surface air temperatures now higher than at any time in at
least 2,000 years. These recent trends since the Industrial Revolution cannot be explained
by orbital variations or by solar luminosity. In fact, these two natural external forcing agents
should be gently nudging us into a cooling phase.
As was foreseen by climate models as early as 1980, the Arctic is warming faster than
any other region on the planet (with the possible exception of some parts of the Antarctic
Peninsula). Since the late 1960s, the surface temperature has been increasing at a rate of ap-
proximately 0.4°C per decade. In Alaska and western Canada, the ACIA noted that average
winter temperatures have risen by between 3 and 4°C.
The air surface temperature anomalies in the Arctic are more than twice those recorded
at most lower latitudes and are found over land and ocean and in summer and winter. Look-
ing further back, Martin Tingley and Peter Huybers have recently published a study using
paleoclimate proxies (such as tree ring, ice core isotopes and lake sediment records) to re-
construct previous Arctic temperatures. They concluded that the summers of 2005, 2007,
2010 and 2011 were warmer than those at any other time since at least the year 1400. Re-
gional patterns of Arctic surface air temperature anomalies according to the seasons are also
emerging, with some areas showing more intense warming than others. This seasonality is
illustrated in Figure 10.5 .