Climate Change in the Arctic - The Changing Arctic Environment: The Arctic Messenger - page 241

SomeofthecandidatesrelatetohowEarthorbitsthesun.Thisisknownas orbital for-
cing . The three best-known types of orbital forcing are collectively called the Milankovitch
cycles . They have played a key role in the starting and ending periods of glaciation. Al-
though the seasonal and higher-latitude climate forcing by orbital cycles is large, the net
forcing is close to zero in terms of the global mean. They operate over thousands of years.
Together with our present situation of being in relatively “benign” parts of the cycles, this
makes them very unlikely candidates for being responsible for the present global warming
reported by the IPCC. If you are interested, you will find a fuller description of orbital for-
cing in Appendix IV .
Variations in solar intensity (brightness) are natural processes that can make our world
warmer and colder. Could they be responsible for any climate changes being observed
today? Solar intensity is roughly linked to the sunspot cycle that has a periodicity of about
11 years. A spotty sun is a warmer sun, and overall, the cycle alters the intensity by about
0.08%. The Little Ice Age, which ran from as early as 1350 and that some experts consider
did not end until about 1850, is believed to have been a time when the sun carried fewer
sunspots. Within this period is the Maunder Minimum, from 1645 to 1750, when no sun-
spots were recorded. When Sir John Franklin was sent off by the British admiralty to find
and transit the Northwest Passage in 1845, it did not pick the most auspicious time in terms
of varying solar intensity. Franklin overwintered in 1845-1846 beside Beechey Island at
the south-west corner of Devon Island. Three young crewmen died there and were buried
with marked graves. Their bodies were given autopsies in the 1980s, when they were found
to be carrying unusually high levels of lead, probably coming from the lead solder used to
seal their canned foods and from the water distillation equipment carried on the ships. The
men were later returned to their graves. I have only been ashore there once, landing in a
Twin Otter equipped with skis. The gravestones were just visible above the soft snow. It is
an evocative spot and a poignant reminder of the follies of history. In the summer of 1846,
the Franklin expedition left Beechey Island on the Erebus and the Terror and sailed into
oblivion. Although Franklin's fate is now somewhat understood, it was not until 2014 that
one of his ships ( HMS Erebus ) was found.