Global Warming

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Global Warming

Global warming is real , and human beings have something to do with it We don 't have everything to do with it but we can 't stop it , and we couldn 't even slow it down enough to measure our efforts if we tried

Whether a person believed in an earth-centered universe or a heliocentric one (a view of Jupiter and its moons soon convinced

Galileo of the latter , everyone pretty

much agreed that the sun warmed the earth . So the appearance of black spots became a curiosity worth recording : Would a darker sun create a cooler planet

We now know that the opposite is true . A sun with many spots is a hotter sun because the dark regions are surrounded by larger , whiter areas that are more energetic than the quiescent state . Since that discovery myriad scientists have matched the earth 's temperature to the output of the sun . This isn 't exactly rocket science . If there were no match , the basic theory of climatology would be wrong , a theory that simply states that the sun is the cause of our climate

A review of sunspot records is one way to back-calculate the earth 's temperature before the general use of thermometers , which dates back to the mid-1800s . But there are other climate proxies (Webb Overpeck , 1993

The width of tree rings , for example , is related to summer temperature . Plants leave fragments , including long-lasting pollen , in the bottom of lakes , and shallow lakes turn over ' every year , creating annual striations , called varves , that can be counted back in time . Shifts in pollen assemblages trapped in varves from boreal (spruce , fir , birch - the north woods ' complex ) to oak and pine , for example , would characterize a warming climate

Something happened . But what ? Why didn 't the divergence between solar-derived and greenhouse-enhanced temperatures begin earlier

First , the early increments of CO 2 were relatively small . After accounting for the known constellation of greenhouse-enhancing gases only about a third of the In the absence of an atmosphere , it 's pretty easy to calculate the temperature of the earth-atmosphere system . All you need to know is the amount of radiation that the earth intercepts from the sun and the amount that it reflects from its non-black surface . That number works out to about 17 ?C (1 .4 ?F

But obviously , that 's not the correct surface temperature . In large part , that 's because the gases in our atmosphere selectively absorb some of the sun 's incoming radiation as well as another fraction of the heat emanating from the sun-warmed earth . Those molecules , such as oxygen water vapor , and carbon dioxide , ultimately release that energy preferentially warming some layers of the atmosphere at the expense of cooling elsewhere

Carbon dioxide and water vapor are especially adept in absorbing the heat of the earth 's surface . When they release (or re- radiate ) that energy , they do so...