    Latest Posts
|
 It cooled mid-centuryAbout 1940, just as man-made CO2 emissions rose sharply, the temperature began dropping right until the 1970's. If CO2 is the driving force of global warming, why did temperatures fall when CO2 emissions rose? What the science says...CO2 is not the only factor controlling global temperatures. The sun is the major driver of climate but solar levels been steady for the past 50 years. Another significant factor is aerosols (tiny particles suspended in the air) that have a cooling effect by reflecting sunlight (this is called global dimming). The more aerosols in the atmosphere, the less sunlight reaches the Earth's surface. Surface measurements of solar radiation found a global trend of dimming from 1960 which reversed around 1985. From that point, there has been a general trend of brightening. As solar output has been steady over this period, this is consistent with measurements of aerosol levels that have fallen since the early 80's. Note - this doesn't explain current warming but does explain why CO2 warming has been masked from 1950 to 1980. Satellite measurements of solar radiation at the Earth's surface has detected a long term increase in surface brightness from 1983 to 2001. Combined with the fact that solar levels have been level since the 50's, this indicates aerosol levels have been falling. Further readingOpen Mind has an interesting post Hemispheres that compares temperature records for both hemispheres over the past century and the significance for mid-century cooling.
Post a CommentFoul language, trolling, personal attacks or non-relevant links will be deleted. You need to be logged in to post a comment. Login via the left margin or if you're new, register here.
|
| © John Cook 2008 | |
 |
|
The skeptic argument...