Monday, March 30, 2009
New York Times bestselling author Gregg Braden claims that climate change is largely driven by the strength of the Earth's magnetic shield at any point in time.
Only a couple of months ago, NASA discovered an unprecedented breach in the Earth's magnetic shield (watch the NASA video), and the strength of the magnetic shield is known to vary in intensity over geologic time. So this is an interesting claim.
My question to you is whether anyone has ever attempted to correlate the Earth's magnetic field strength with climate changes. My layman's logic wonders whether a reduction in field strength of 10% would result in some additional solar energy reaching the atmosphere, and hence cause an increase in overall global temperatures. I understand that the geologic record of magnetic field strength may span far more time than the records of global temperature in the polar ice core samples (or however those estimates are made), but has any attempt at correlation of the data been made?Any scientists wishing to weigh in on this question can comment below.
The "solar energy" received by Earth presumably includes sunlight and the solar wind (with the magnetic effects it brings with it). Let us compare.
Suppose the Earth had NO magnetism at all, so that the solar wind would hit its surface directly--as it hits the Moon, most of the time. The solar wind has a density of about 6 protons per cc, and velocity about 400 km/sec, so each square centimeter facing it is hit each second by as many protons as are in a column about 400 kilometers high and of 1 square centimeter cross section:
400,000 x 100 x 6 = 2.4 x 100,000,000 protons and each square meter (10,000 times larger) about 2.4 1012 protons
Each proton carries about 1000 electron volts, each of which is abut 1.6 10–19 joule So that each square meter gets about 4 10–4joules per second, that is, 0.0004 watt.
The "solar constant" of sunlight energy received by a square meter on the Earth perpendicular to sunlight is about 1300 watt. It's more than a million times larger.
The changing strength of the Earth's magnetic field may have less effect than its magnitude suggests. That field diverts the solar wind around the Earth, though some energy is transmitted in other ways, through reconnected field lines. If the field were only half as strong, the obstacle would be smaller, but still, most of the solar wind would flow around. The total effect remains roughly the same as before--that sunlight is more than a million times more effective as carrier of energy.