By Paul Homewood
The Mail gives uncritical coverage to the latest bit of junk science:
Plant growth has decreased by 59 per cent worldwide since 1999 due to a lack of water in the atmosphere, a new study suggests.
Experts studied four global climate datasets to try and uncover why vegetation growth has stalled in the past two decades.
They found that a drop in levels of water vapour had stopped plants from being able to photosynthesise.
Photosynthesis is used by plants, some bacteria and single-celled organisms to draw energy from sunlight, taking in carbon dioxide and water in the process.
Researchers from Sun Yat-sen University in Zhuhai, China, found that the decline is linked to a vapour pressure deficit (VPD) in the atmosphere.
VPD is the difference between the pressure that would be exerted by water vapour when the air is fully saturated and the pressure it actually exerts.
This has increased sharply over more than 53 per cent of vegetated areas since the late 1990s.
When this deficit increases, the pores on the surface of leaves that taken in carbon dioxide and release water vapour close up, resulting in lower rates of photosynthesis.
These findings, however, are in stark contrast to a study in 2016, which found that the world had massively been greened by extra CO2 in the atmosphere, as the BBC reported:
Carbon dioxide emissions from industrial society have driven a huge growth in trees and other plants.
A new study says that if the extra green leaves prompted by rising CO2 levels were laid in a carpet, it would cover twice the continental USA.
Climate sceptics argue the findings show that the extra CO2 is actually benefiting the planet.
But the researchers say the fertilisation effect diminishes over time.
They warn the positives of CO2 are likely to be outweighed by the negatives.
The lead author, Prof Ranga Myneni from Boston University, told BBC News the extra tree growth would not compensate for global warming, rising sea levels, melting glaciers, ocean acidification, the loss of Arctic sea ice, and the prediction of more severe tropical storms.
The new study is published in the journal Nature Climate Change by a team of 32 authors from 24 institutions in eight countries.
It is called Greening of the Earth and its Drivers, and it is based on data from the Modis and AVHRR instruments which have been carried on American satellites over the past 33 years.The sensors show significant greening of something between 25% and 50% of the Earth’s vegetated land, which in turn is slowing the pace of climate change as the plants are drawing CO2 from the atmosphere.
Just 4% of vegetated land has suffered from plant loss.
We have, of course, often been warned that a warmer atmosphere can hold more water vapour, which is then blamed for heavier rainfalls.
Now they are trying to argue that the air is drier!
There is one key chart in this new paper, which underlines just how bad it is. It concerns oceanic evaporation, which is the most important factor, as the paper explains:
A change of oceanic evaporation is the most important mechanism for the observed decrease in actual water vapor pressure over the land (18). Oceanic evaporation is the most important source of atmosphere water vapor, and approximately 85% of atmospheric water vapor is evaporated from oceans, with the remaining 15% coming from evaporation and transpiration over land (19). Most of the moisture over land is transported from the oceans, which accounts for 35% of precipitation and 55% of evapotranspiration over land (19).
And what does the graph show?
A drop in evaporation in the 1960s and 70s, when the world was cooling, followed by a rise when the PDO and AMO kicked into warm phases, thus leading to a warming period.
And since 1998, another drop. This incidentally indicates that oceanic warming has stopped since 1998, which would confirm the global temperature pause still evident from satellite measurements. Physics, after all, tells us that warmer oceans lead to increased evaporation.
Either way, it is clear that we have a cyclical pattern, and that reduced evaporation since 1998 has nothing at all to do with global warming. Indeed, quite the opposite – when the world was warming between 1979 and 1998, evaporation increased.
But if they admitted that, they would quickly kiss goodbye to their next grant cheque!
This article appeared on the Not A Lot of People Know That website at https://notalotofpeopleknowthat.wordpress.com/2019/08/16/global-vegetation-decreasing-as-the-world-gets-greener-or-something-like-that/#more-40931