Causes Of Natural Climate Change In The Past

In this post, I will discuss about the natural climate change contributors in the past, and still contributing big nowadays. This is just a summary post of global warming and natural climate change in the past article.

Solar activity
Solar variations have been the major driver of climate change over the past 10,000 years. Similarly, solar activity was higher during the Medieval Warm Period.
However, the correlation between solar activity and global temperatures ended around 1975. At that point, temperatures started rising while solar activity stayed level. This led a team of scientists from Finland and Germany to conclude "during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source." More on the sun & global warming.

Milankovitch cycles
Earth's climate undergoes 120,000 year cycles of ice ages broken by short warm periods called interglacials. The cycle is driven by Milankovitch cycles. Long term changes in the Earth's orbit trigger an initial warming which warms the oceans and melts ice sheets - this releases CO2. The extra CO2 in the atmosphere causes further warming leading to interglacials ending the ice ages.
The current trend of the Milankovitch cycle is a gradual cooling down towards an ice age.

Volcanoes
Volcanic eruptions spew sulfate aerosols into the atmosphere which has a cooling effect on global temperatures. These aerosols reflect incoming sunlight, causing a 'global dimming' effect. Strong volcanic activity exacerbated the Little Ice Age in the 1800's.

Summary
The usual suspects in natural climate change - solar variations, volcanoes, Milankovitch cycles - are all conspicuous in their absence over the past 3 decades of warming. This doesn't mean by itself that CO2 is the main cause of current global warming - you don't prove anthropogenic warming by eliminating all other options. But the primary causes of commonly cited climate change in the past have played little part in the current warming trend.
As for CO2, empirical observations show that CO2 has a warming effect as a greenhouse gas, CO2 is increasing in the atmosphere and the expected warming you would get from greenhouse gases is occurring.

Further explanation and information will be posted here. I suggest that you stay tuned for more updates. Meanwhile, read the whole article prior to this post at global warming and natural climate change in the past webpage.

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