Earth's clouds are shifting towards its poles

LOL!  By applying heavy "corrections" to their data they got a story that would correspond to global warming theory.  I don't know where to start here, it's such a hoot.  Could there have been some bias in the "corrections"?  One would have to be naive to dismiss it.

And why did they not segregate their data into the 20th and 21st centuries?  If their theories are right that would have been a splendid way to test them. If the clouds kept moving polewards in C21, that would disprove their theory -- as there was no statistically significant warming in C21 until last year.  They obviously did NOT want to test their theory.

And what they say is wrong anyway. They found "growing dry regions" as rain-bearing clouds move polewards.  But what about the Sahel?  The Sahel is actually in the tropics so should be very strongly affected by what they claim.  And it is a very large dry region so would seem an excellent test of their theory.  So has the Sahel got any drier?  To the contrary, it has shrunk in recent years.  Much that was once desert is now green.   That's one test of their junk theory that they could not fudge -- and the theory fails its test abjectly

Journal article appended

Bands of cloud cover that swirl around the globe are slowly creeping towards the poles, causing dry regions to expand around the equator, climate scientists have warned.

Using satellite data captured between the 1980s and 2000s, researchers found that channels of cloud cover which carry storms around the globe have shifted closer to the poles over time.

As well as poleward shift in cover and expanding dry regions, they findings show the height of cloud tops have increased at all latitudes, all of which impacts on the global climate and agree with predictions for the impact of climate change.

Cloud cover is a key factor in regulating the planet's temperature, with cover reflecting solar radiation back into space or acting as a blanket to keep surface heat from escaping, depending on the type and thickness of clouds.

But while the effects of such a variable system are almost impossible to decipher in the short term, over a period of decades long-term trends begin to emerge.

Led by climate scientists at the University of California, the team was able to correct the satellite data from several sources to show such long term trends, removing errors and inaccuracies from satellite sensors and erroneous trends.

They found that dry bands over the subtropical regions are expanded – a belt which covers regions including the Southern United States, North Africa and Central Australia – and the height of cloud tops at all latitudes has increased.

Climate scientists in the US looked at several datasets going back to the early 1980s.

By removing errors caused by satellite sensors, incorrectly calibrated systems and countering for erroneous trends, they were able to show long-term trends in cloud coverage.

They found the band of clouds which carries tropical storms around the planet have moved from the subtropical regions towards the poles.

But in their wake, they have further opened up dry areas in subtropical regions – in a belt which covers regions including the Southern United States, North Africa and Central Australia.

What's more, they found the height of cloud tops at all latitudes has increased.

The researchers have said that their observations align with predictions previously made in complex climate models.

They say the findings agree with climate models, which predict a warming climate will be accompanied with less cloud coverage in the tropics and growing dry regions.

'What this paper brings to the table is the first credible demonstration that the cloud changes we expect from climate models and theory are currently happening,' said Professor Joel Norris, a climate scientist at the Scripps Institute for Oceanography in California, who led the research.

According to the researchers, the effect on cloud cover has been caused by a combination of greenhouse gases from human activity over several decades.

But compounding this warming effect is the bounce back from two large volcanic eruptions – the El Chichón eruption in Mexico in 1982 and the 1991 eruption of Mount Pinatubo in the Philippines – which had a far reaching cooling effect on the climate.

When combined, these two factors result in a positive feedback loop, warming the climate.


Evidence for climate change in the satellite  cloud record

Joel R. Norris et al


Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts.

Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

SOURCE.  [doi:10.1038/nature18273]

No comments:

Post a Comment

All comments containing Chinese characters will not be published as I do not understand them