Changes

According to temperature reconstruction made within an [[Old Earth]] paradigm, there have been many cycles of naturally-caused global warming and cooling over many millions of years (see [[climate cycles]]). Some scientists, including [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent), say that the recent warming could be part of another natural cycle or random fluctuations in the atmosphere. However, many scientists also think that human activities were most likely the cause of the the planet's recent warming.

According to temperature reconstruction made within an [[Old Earth]] paradigm, there have been many cycles of naturally-caused global warming and cooling over many millions of years (see [[climate cycles]]). Some scientists, including [[Richard Lindzen]] of [[MIT]], [[Sallie Baliunas]] of [[Harvard]] and [[Fred Singer]] (independent), say that the recent warming could be part of another natural cycle or random fluctuations in the atmosphere. However, many scientists also think that human activities were most likely the cause of the the planet's recent warming.

Recent studies of the Milankovich Cycles, which predict Earth's climate by studying changes in its orbit and axial tilt, suggest that we are currently 18,000 years into a 150,000 year period between ice ages. This would imply that we should expect the temperature to be rising anyway. A 2002 study by Berger and Loutre suggests 50,000 years of warmer weather before Earth begins to cool again, which fits exactly with these predictions and implies that the temperature is rising naturally die to the cycles rather than human activity.

Recent studies of the Milankovitch Cycles, which predict Earth's climate by studying changes in its orbit and axial tilt, suggest that we are currently 18,000 years into a 150,000 year period between ice ages. This would imply that we should expect the temperature to be rising anyway. A 2002 study by Berger and Loutre suggests 50,000 years of warmer weather before Earth begins to cool again, but that model incorroprated anthropogenic forces and concluded:

<blockquote>While combinations of natural forcings produce a gradual warming up to about 1960, none of them leads to a warming over the last 30 years (this period containing three major volcanic eruptions). In contrast, simulations incorporating only anthropogenic forcings reproduce the warming over the last three decades at a rate consistent with that observed, but underestimate the early 20th century warming. As a consequence, only the use of both natural and anthropogenic forcings allows to reproduce much of the observed decadal scale variations of the annual mean hemispheric temperature over the last 150 years.<ref>[http://onlinelibrary.wiley.com/doi/10.1034/j.1600-0870.2002.00287.x/full] Climate of the last millennium: a sensitivity study, May 2002</ref></blockquote>

 

It should be noted, however, that computer simulated climate models are often tweaked so they agree with the historical temperature record. There is no way to completely simulate all of the Earth's climate with a computer program.

== Sun Spots ==

== Sun Spots ==