"Cato" wrote
Welcome to Earth.. where climate has been
changing for hundreds and thousands of millions of years.

Cato engages in GW Denialist Fraud Type 2

Fraud type 2
Global warming and natural climate change in the past

What the science says...

It's a well established fact that climate changes naturally and sometimes
dramatically. The pertinent question isn't "has climate changed in the
past?" (of course it has) but "what is causing global warming now?" To begin
to answer that, it's helpful to look at the major causes of natural climate
change in the past.

Solar activity
Solar variations have been the major driver of climate change over the past
10,000 years. When sunspot activity was low during the Maunder Minimum in
the 1600's or the Dalton Minimum in the 1800's, the earth went through
'Little Ice Ages'. 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.



For the past 12,000 years, we've been in an interglacial. 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. Usually, the cooling effect
lasts several years until the aerosols are washed out of the atmosphere. In
the case of large eruptions or a succession of eruptions such as in the
early 1800's, the cooling effect can last several decades. Strong volcanic
activity exacerbated the Little Ice Age in the 1800's.

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 causes of the commonly cited climate
changes in the past are understood and have played little to no part in the
current warming trend.