China’s coldest winter in 100 years, Baghdad’s first snow in recorded history, North America has the most snow cover in 50 years. Record cold in Mexico, Australia, Iran, Greece, South Africa, Greenland, Argentina, Chile … in the past 12 months, global temperatures have dropped so dramatically that a century of warming has been reversed. Why? And where do we go from here?

This graph, compiled by the UK Met Office’s Hadley Centre for Climate Prediction, shows monthly world temperatures logged from 1988 to 2008. (Click it for a larger image.) The implication of the blue bit at the end is that in just the past twelve months, global temperatures changed so much that the warming of the previous century has all but been negated — wiped out, in the words of Michael Asher, writing in DailyTECH on 26th February 2008.

This amazing fall in global temperatures has also been noted by NASA’s GISS (Goddard Institute for Space Studies), RSS (Remote Sensing Systems of Santa Rosa) and UAH (University of Alabama, Huntsville). For all four sources, says Asher, it’s the single fastest temperature change ever recorded, either up or down.

Increasingly, scientists are linking this drop in temperature to solar activity — or rather, the lack of it. I’ve just checked the SpaceWeather.com archives, and there have been no follow-up sunspots that would indicate an increase in solar activity since the first “official” sunspot of 4th January 2008 that kicked off Solar Cycle 24 — supposedly our next period of high solar activity. The Sun remains stubbornly quiet. We’ve been through this before — 400 years ago. It led to a solar event known as a “Maunder Minimum,” which in turn caused what we now call the “Little Ice Age.”

In another DailyTECH item (dated 9th February 2008), Asher neatly summarises the concerns of Dr. Kenneth Tapping, a solar researcher and project director at Canada’s National Research Council: if the pattern doesn’t change quickly, the Earth is in for some very chilly weather.

Chilly, indeed: during the Little Ice Age, people could walk across a frozen New York Harbor from Manhattan to Staten Island. In Britain, eskimos were reported to be seen paddling canoes off the coast. In Norway, glaciers grew up to 100 metres a year, bringing inexorable destruction to farms and villages.

Tapping is not the first researcher to highlight the dangers of solar inactivity, says Asher. In 2005, Russian astronomer Khabibullo Abdusamatov predicted the Sun would soon peak, triggering a rapid decline in world temperatures. Only last month, the view was echoed by Dr. Oleg Sorokhtin, a fellow of the Russian Academy of Natural Sciences, who advised the world to “stock up on fur coats.” Sorokhtin, who calls man’s contribution to climate change “a drop in the bucket,” predicts the solar minimum to occur by the year 2040, with icy weather lasting till 2100 or beyond.

During periods of high solar activity, the Sun’s solar wind — a plasma (an ionised gas consisting mainly of protons and electrons) which flows outward in all directions from the Sun’s surface and envelops the Earth, and which conveys with it the Sun’s magnetic field — is strengthened. If this solar wind could strike the Earth unhindered, life as we know it could never exist here. Fortunately, Earth has a protective barrier in the form of its magnetosphere — its own natural magnetic field, which extends out into space around our planet.

As well as protecting us from the solar wind by deflecting it around the Earth, it’s thought that this magnetic “blanket” also prevents an excess of cosmic rays from deep space striking our atmosphere — especially when the two act in concert, like a double protective layer. Some scientists believe that cosmic rays play a part in cloud formation — fewer rays equal less cloud-cover, allowing more heat from the Sun to reach our planet and warm it up. When the Sun is quiet, its solar wind is correspondingly weakened, allowing more cosmic rays to interact with the Earth’s atmosphere and form more clouds. These reflect more of the Sun’s heat back into space, and we cool down.

According to the NOAA’s National Geophysical Data Center, the Earth’s magnetic field is weakening and may even be en route to completely flipping (this doesn’t mean the Earth would physically flip over 180 degrees, only that the magnetic poles would reverse, swapping their geographical locations). This has happened many times in our planet’s past, and the evidence for it can be found in certain rocks that “remember” the direction of the Earth’s magnetic field when they were created. Some think that the point where the field reaches its flipping point is about 1,300 years away, and it would then take about 7,000 years to rebuild itself. During the past 100 million years, reversal rates have varied considerably. Recent rock records indicate reversals occurring on time scales of about 200,000 years. The last time the magnetic field reversed was about 750,000 – 780,000 years ago.

No-one knows for sure what effect a weakening magnetic field would have on our protective blanket. Perhaps Earth would still have a magnetic field during a reversal, but it would be weaker than normal with multiple magnetic poles. Radio communication would deteriorate, navigation by magnetic compass would be difficult and migratory animals might have problems.

And perhaps a weakening magnetosphere, combined with a quiet solar wind, will allow in more cosmic rays which will create more clouds, causing an accelerated cooling of the Earth …

Hang on — isn’t this where we came in?

Read my Climate Change posts in chronological order by using the Climate Change Log.

Tags: Climate Change, Solar Activity

This entry was posted on Friday, March 7th, 2008 at 3:48 pm and is filed under Climate Change. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.