单选题 The strangest weather of last year was possibly not on Earth, but on the Sun. Every 11 years 31 the Sun goes through a cycle of sunspots--actually magnetic storms erupting across its surface. The number of sunspots 32 its minimum in 2007 and 33 have increased soon afterwards, but the Sun has remained strangely quiet since then. Scientists have been baffled as weeks and sometimes months have gone by without a single sunspot, in 34 is thought to be the deepest solar minimum for almost 100 years.
This 35 of solar activity means that cosmic rays reaching Earth from space have increased and the planet"s ionosphere in the upper atmosphere has sunk in 36 , giving less drag on satellites and making collisions between them and space junk more likely. The solar minimum could also be cooling the climate on Earth because of slightly diminished solar irradiance. In fact, the quiet spell on the Sun may be 37 some of the warming effects of greenhouse gases, accounts for the somewhat flat temperature trend of the past decade. But 38 if this solar minimum is offsetting global warming, scientists stress that the overall effect is relatively slight and certainly will not last.
The Sun has gone into long quiet spells before. From 1645 to 1715 few sunspots were seen during a period called the Little Ice Age, when short summers and savage winters often plagued Northern Europe. Scotland was hit particularly 39 as harvests were ruined in cold, miserable summers, which led to famine, death, migration and huge depopulation. But whether the quiet Sun was entirely to blame for it remains highly 40 .