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Sunspots and global weather


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The last solar quiet period produced average drops of about 1°C

The models for global warming predict 1.1 to 6.4 °C by 2100

The estimate is it's already risen 0.75°C over the 20th century

But aren't those estimates based on the current temperature rise being 100% due to CO2 based global warming.

If it is becomming accepeted that maybe sunspot activity will lead to cooling then the very active sunspot period of the 20th Century should account for a proportion of the 20thC warming and hence CO2 would not need to account for all of it, hence the 1.1 to 6.4C for future rise would be an overestimate?

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  • 2 weeks later...

Feulner & Rahmstorf 2010 (PDF here) covers this.

finding a moderate temperature offset of no more than −0.3°C in the year 2100 relative to a scenario with solar activity similar to recent decades. This temperature decrease is much smaller than the warming expected from anthropogenic greenhouse gas emissions by the end of the century.

See also articles on it here (from the previous round of this meme), here (with video debunking the "news" articles about this) and here (blog post by the lead author of the above paper).

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From the OP:

New Little Ice Age in store? - Telegraph - "The Earth could enter a new 'Little Ice Age' in the coming years due to low solar activity, astronomers believe. "

Yet the only one they quote about that says precisely the opposite: "Even if the predictions [of an extended solar minimum] are correct, the effect of global warming will outstrip the sun’s ability to cool even in the coldest scenario. "

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Edit: There is a stronger effect on northern European winters than there is globally, because solar minimum can affect the path of the jet stream: Lockwood et al, 2010: Are cold winters in Europe associated with low solar activity?.

We show that cold winter excursions from the hemispheric trend occur more commonly in the UK during low solar activity, consistent with the solar influence on the occurrence of persistent blocking events in the eastern Atlantic. We stress that this is a regional and seasonal effect relating to European winters and not a global effect.
Edited by Dave R
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But aren't those estimates based on the current temperature rise being 100% due to CO2 based global warming.

No, all the known forcings are taken into account. Also bear in mind the major uncertainty in that quoted range is future emissions. For a doubling of CO2 the expected global mean temperature rise is 2 to 4.5 degrees with a best estimate of 3.

If it is becomming accepeted that maybe sunspot activity will lead to cooling

It isn't, as demonstrated above.

then the very active sunspot period of the 20th Century should account for a proportion of the 20thC warming

Solar variation did account for a proportion of the warming in the early part of the 20th century, but not in the second half, as solar activity did not increase during the second half.

Edited by Dave R
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Although I can't remember where, I read once that during the Maunder Minimum of the early 17th Century summers were so cold that crops did not grow and that famine in Europe resulted in increases in disease which might have magnified the impact of the bubonic plague. This would have been during the earliest colonization of America. The same source said that the very cold temperatures drove migration from New England to the South and West in search of climates that would produce sufficient crops to support population growth.

If that information is accurate - and if the Earth were to experience a similar climatic change due to reduced solar activity - I believe that global temperatures would drop more than the 20th Century increase. This typifies why assessing the true impact of industrialization and CO2 gas releases if nigh impossible. Prudence and a conservative (ie, non-wasteful) nature impel me toward the need for reduced CO2 emissions - far more than any clear evidence of the global warming alarmists.

Our Ted Turner was quoted in the press yesterday as saying that global warming from CO2 emissions is the greatest threat humankind has ever faced. That smacks too much of Chicken Little to be credible to me.

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