BBC: Rise in CO2 has ‘greened Planet Earth’ – ‘Plant boom’
Nic Lewis, an independent scientist often critical of the IPCC, told BBC News: "The magnitude of the increase in vegetation appears to be considerably larger than suggested by previous studies. "This suggests that projected atmospheric CO2 levels in IPCC scenarios are significantly too high, which implies that global temperature rises projected by IPCC models are also too high, even if the climate is as sensitive to CO2 increases as the models imply." And Prof Judith Curry, the former chair of Earth and atmospheric sciences at the Georgia Institute of Technology, added: "It is inappropriate to dismiss the arguments of the so-called contrarians, since their disagreement with the consensus reflects conflicts of values and a preference for the empirical (i.e. what has been observed) versus the hypothetical (i.e. what is projected from climate models). "These disagreements are at the heart of the public debate on climate change, and these issues should be debated, not dismissed."
The new study is published in the journal Nature Climate Change by a team of 32 authors from 24 institutions in eight countries.
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 authors note that the beneficial aspect of CO2 fertilisation have previously been cited by contrarians to argue that carbon emissions need not be reduced.
Co-author Dr Philippe Ciais, from the Laboratory of Climate and Environmental Sciences in Gif-sur‑Yvette, France (also an IPCC author), said: “The fallacy of the contrarian argument is two-fold. First, the many negative aspects of climate change are not acknowledged.
“Second, studies have shown that plants acclimatise to rising CO2 concentration and the fertilisation effect diminishes over time.” Future growth is also limited by other factors, such as lack of water or nutrients.
The scientists say several factors play a part in the plant boom, including climate change (8%), more nitrogen in the environment (9%), and shifts in land management (4%).
But the main factor, they say, is plants using extra CO2 from human society to fertilise their growth (70%).
Harnessing energy from the sun, green leaves grow by using CO2, water, and nutrients from soil.