[orionblamblam]

Since the late 19th century (certainly the mid-1800's), the northern hemisphere has gotten warmer. The Thames used to freeze solid. Snow would get dozens of feet deep regularly in some places.

This warming trend is a result of finally breaking out fo the Little Ice Age.

[megatherium]

There's interesting evidence for the sun being linked to the Little Ice Age: there were no sunspots for 70 years in the 17th century (the Maunder Minimum). The sun puts out more energy when it has more sunspots.

The climate is changing, though, regardless of the cause. Temperatures at high latitudes have increased by several degrees; glaciers world-wide are in retreat. Glacier National Park is going to be poorly-named in several decades if this continues. Mt. Kilimanjaro is losing its glacier as well: by 2020 if trends continue, it will be gone. This glacier is 12,000 years old. (However, a drop in precipitation rather than an increase in temperature seems to be the reason for this.)