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Rising CO2: The Greening Of Planet Earth

Doug L Hoffman, The Resilient Earth

Satellite observations reveal a greening of the globe over recent decades. Increased levels of CO2 have helped boost green foliage across the world’s arid regions over the past 30 years.

While the debate rages regarding global warming and mankind’s role in climate change there is one area that is not in dispute: the steady rise in atmospheric CO2 over the last century. Indeed, climate change alarmists celebrated CO2 readings passing 400ppm at Mauna Loa with news releases and renewed predictions of the coming Apocalypse. But carbon dioxide has other impacts, one of which has recently been documented by the Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia’s national science agency. According to CSIRO, increased levels of CO2 have helped boost green foliage across the world’s arid regions over the past 30 years. This is because of a process called CO2 fertilization, which unequivocally shows that carbon dioxide is plant food.

Based on satellite observations from 1982-2010, CSIRO found that rising atmospheric CO2 levels correlated with an 11% increase in foliage cover across a number of arid areas in Australia, North America, the Middle East and Africa. Performed in collaboration with the Australian National University (ANU), this study determined that the fertilization effect occurs where elevated carbon dioxide enables leaves to extract more carbon dioxide from the air, lose less water to the air, or both during photosynthesis.

“While a CO2 effect on foliage response has long been speculated, until now it has been difficult to demonstrate,” reported Dr Randall Donohue, a CSIRO research scientist. “Our work was able to tease-out the CO2 fertilisation effect by using mathematical modelling together with satellite data adjusted to take out the observed effects of other influences such as precipitation, air temperature, the amount of light, and land-use changes.”

The research was funded by CSIRO’s Sustainable Agriculture Flagship, Water for a Healthy Country Flagship, the Australian Research Council and Land & Water Australia. The study was published in the journal Geophysical Research Letters Here is the paper’s abstract:

Satellite observations reveal a greening of the globe over recent decades. The role in this greening of the “CO2 fertilization” effect—the enhancement of photosynthesis due to rising CO2 levels—is yet to be established. The direct CO2 effect on vegetation should be most clearly expressed in warm, arid environments where water is the dominant limit to vegetation growth. Using gas exchange theory, we predict that the 14% increase in atmospheric CO2 (1982–2010) led to a 5 to 10% increase in green foliage cover in warm, arid environments. Satellite observations, analyzed to remove the effect of variations in precipitation, show that cover across these environments has increased by 11%. Our results confirm that the anticipated CO2 fertilization effect is occurring alongside ongoing anthropogenic perturbations to the carbon cycle and that the fertilization effect is now a significant land surface process.

So, while global temperatures have not risen since the turn of the millennium, noticeable changes in vegetation are evident. As stated, the results were not limited to Australia, the researchers found that arid areas all over the globe were reaping the carbon dioxide bounty, as shown in the map below.

“On the face of it, elevated CO2 boosting the foliage in dry country is good news and could assist forestry and agriculture in such areas; however there will be secondary effects that are likely to influence water availability, the carbon cycle, fire regimes and biodiversity, for example,” Dr Donohue said.

This research does not mean that all the world’s deserts are suddenly springing into bloom, but in the affected areas an 11% increase in plant cover was found. Here is the declaration from the CSIRO website:

In the areas where we could isolate the CO2 effect from the effects of other drivers (such as changes in rainfall, temperature, humidity and land use), we observed an 11 per cent increase in cover. In other areas, where we were unable to isolate the CO2 effect, the overall change in cover will be the net effect of all the driving processes, including CO2fertilisation.

So the CO2 fertilisation effect means that cover is around 11 per cent greater now than it would have been if CO2 levels were constant. In other words, there are places that have become less green (ie lower cover), but they would have had even lower levels of cover had CO2 not increased.

This blog has reported on the beneficial effect of rising carbon dioxide levels on plants before (see “Forests Flourish On Human CO2”). In particular, studies of northern forests documented reduced H2O use with rising CO2 levels. “Our analysis suggests that rising atmospheric CO2 is having a direct and unexpectedly strong influence on ecosystem processes and biosphere–atmosphere interactions in temperate and boreal forests,” reported Trevor F. Keenan et al. in the journalNature back in 2012.

As I reported then, the three most important climate change related factors were increased temperature, increased growing season length, and increased atmospheric CO2 levels. How each of these factors affect forest growth were explained as follows:

  • Increased Temperature. Temperature is critical to all metabolic processes involved in uptake, release, and storage of carbon. Rising temperatures, especially when coinciding with adequate precipitation and without resource limitation, can increase tree metabolic processes that, in turn, lead to higher biomass accumulation.
  • Increased Growing Season. Higher temperatures are also correlated with longer growing seasons. A steady lengthening of the growing season has been documented worldwide, and even a shift in the seasonal phase of surface temperatures has been detected. Growing degree days correlate with the speed of forest recovery from pasture in the Amazon and increased plant growth in boreal forests.
  • Increased CO2Atmospheric CO2 can increase tree growth through carbon fertilization. Trees have shown species-specific increases in growth under elevated CO2, but nutrient and water limitation can slow growth. Measurements of CO2 from SERC match the increases observed from annual averages on Mauna Loa.

Here SERC stands for the Smithsonian Environmental Research Center, where that research was performed. None of this comes as a shock to plant biologists, but climate change alarmists do not wish to hear any good news about rising carbon dioxide levels—can you blame them? Their careers are on the line.

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