June 15, 2011

expert reaction to claim that reduced solar activity could mean that ‘Earth may be headed into a mini ice age within a decade’

Claims circulated by the Global warming Policy Foundation suggest that the sun is entering a period of low activity, which could mean that the Earth could be heading into a ‘mini Ice Age’.

Prof Joanna Haigh, Professor of Atmospheric Physics at Imperial College London, said:

“It’s certainly true that changes in solar activity are likely to influence climate. The sun has well-known cycles, the best known one being the 11-year cycle. But underlying that are longer term variations in its activity.

“This work suggests that the Sun’s activity might be entering a longer period of change – a Grand Minimum, similar to that of the late 17th century (the Maunder minimum). This period is sometimes known as the Little Ice Age, but that is something of a misnomer. First, a real ice age sees huge tracts of land covered in snow and ice year round but that period 300 years ago was nothing like that; temperatures were down in NW Europe by around 1 degree. Second, while this period led to colder temperatures in north-west Europe, over the entire globe it was less than half a degree cooler than normal.

“Predicting the Sun’s activity with accuracy is very difficult. It would certainly be very risky to suggest that we rely on the Sun’s activity to compensate for global warming. In a future Grand Minimum the Sun might perhaps again cool the planet by up to 1 degree. Greenhouse gases, on the other hand, are expected to raise global temperatures by between 1.5 and 4.5C by 2100.

“So even if the predictions are correct, the effect of global warming will outstrip the sun’s ability to cool even in the coldest scenario; and in any case, the cooling effect is only ever temporary. When the Sun’s activity returns to normal, the greenhouse gases won’t have gone away.”

See: http://www.thegwpf.org/science-news/3208-earth-may-be-headed-into-a-mini-ice-age-within-a-decade.html Original work appears to have originated from presentations yesterday at the annual meeting of the American Astronomical Society’s Solar Physics Division in Las Cruces, New Mexico: http://astronomy.nmsu.edu/SPD2011/schedule.html and we think the works in question were posters, see e.g. P16.10 (Frank Hill) or P17.43 in: http://astronomy.nmsu.edu/SPD2011/PROGRAM/spdabstracts/SPD_ebook.pdf