Matt Ridley: Now Here’s The Good News On Global Warming

  • Date: 19/10/15
  • Matt Ridley, The Times

Activists may want to shut down debate, but evidence is growing that high CO2 levels boost crops and nourish the oceans

France’s leading television weather forecaster, Philippe Verdier, was taken off air last week for writing that there are “positive consequences” of climate change. Freeman Dyson, professor emeritus of mathematical physics and astrophysics at the Institute of Advanced Study in Princeton, declared last week that the non-climatic effects of carbon dioxide are “enormously beneficial”. Patrick Moore, a founder of Greenpeace, said in a lecture last week that we should “celebrate carbon dioxide”.

Are these three prominent but very different people right? Should we at least consider seriously, before we go into a massive international negotiation based on the assumption that carbon dioxide is bad, whether we might be mistaken? Most politicians today consider such a view to be so beyond the pale as to be mad or possibly criminal.

Yet the benefits of carbon dioxide emissions are not even controversial in scientific circles. As Richard Betts of the Met Office tweeted last week, the “CO2 fertilisation effect” — the fact that rising emissions are making plants grow better — is not news and is discussed in the reports of the Intergovernmental Panel on Climate Change. The satellite data show that there has been roughly a 14 per cent increase in the amount of green vegetation on the planet since 1982, that this has happened in all ecosystems, but especially in arid tropical areas, and that it is in large part due to man-made carbon dioxide emissions.

Last week also saw the publication of a comprehensive report on “Carbon Dioxide — the Good News” for the Global Warming Policy Foundation by the independent American scientist Indur Goklany, to which Freeman Dyson wrote the foreword. The report was thoroughly peer-reviewed, as was almost all of the voluminous literature it cited. (Full disclosure: I helped edit the report.)

Goklany points out that whereas the benefits of carbon dioxide are huge and here now, the harms are still speculative and almost all in the distant future. There has so far been — as the IPCC confirms — no measurable increase in droughts, floods or storms worldwide, no reversal in the continuing rapid decline in deaths due to insect-borne diseases, and no measurable impacts of the continuing very slow rise in global sea levels. In stark terms, Bangladesh is still gaining land from sedimentation in its rivers’ deltas, has suffered no increase in cyclones, but has benefited from reduced malnourishment to the tune of billions of dollars from higher crop yields as a result of carbon dioxide emissions.

It is worth remembering that commercial greenhouses buy carbon dioxide to enhance the growth of plants, so the growth responses are well known — and it’s not until carbon dioxide reaches five times current concentrations that the benefits level out. As Patrick Moore pointed out, those were normal levels for much of earth’s history.

In addition, hundreds of “free-air concentration experiments” have measured how much increased carbon dioxide levels enhance crop yields in open fields. So it is fairly easy to work out how much carbon dioxide emissions are helping world agriculture: by about $140 billion a year, or $3 trillion in total so far. If reparations are to be paid, perhaps farmers should pay coal producers (full disclosure: I’m both).

Actually, this may be an underestimate: experiments show that crops tend to benefit more than weeds (most crops have a more responsive kind of photosynthetic machinery called C3, while weeds mostly have a less responsive kind called C4). Increased carbon dioxide enhances drought resistance in plants, benefiting dry regions such as the Sahel, which has greened significantly in recent decades. And Goklany calculates that we need 11-17 per cent less land for feeding the world than we would if we had not increased carbon dioxide levels: so emissions have saved — and enhanced the growth of — a lot of rainforest.

Well, all right, but surely the climate harms will one day outweigh the growth benefits? Not necessarily. At the moment, impacts from the modest warming we saw in the 1980s and 1990s are also positive: slightly fewer premature deaths, which peak in cold weather more than in hot weather, slightly longer growing seasons and so on. A paper published last week concludes that if the world does warm significantly, China’s rain systems will shift north, increasing rainfall in the dry north and reducing flooding in the hot south.

Besides, human adaptation means we can capture the benefits and avoid the harms. The IPCC’s forecast warming range includes the possibility that we will still be enjoying net benefits by the end of the century, when the world will (it says) be three to 16 times richer per capita. The fastest way to cut deaths from bad weather today (such as the storm that just battered the Philippines) is to make people richer, not to make weather safer: we have already cut world death rates from droughts, floods and storms by 98 per cent in the past century.

As Goklany demonstrates, the assessments used by policy makers have overestimated warming so far, underestimated the direct benefits of carbon dioxide, overestimated the harms from climate change, and underestimated the human capacity to adapt.

Well, what about the ocean? Here too there’s good news. More carbon dioxide means faster growth rates of photosynthesisers in the sea as well as on land, an effect that is being observed in algae, eelgrasses, corals and especially plankton, such as the abundant creatures known as coccolithophores, whose biomass has increased by 40 per cent in the last two centuries.

That’s not to say coral reefs and fisheries are not in trouble — they are, but because of pollution, overfishing and run-off, not carbon dioxide. The tiny reduction in alkalinity (misleadingly termed “acidification”) caused by dissolved carbon dioxide is potentially negative in the distant future, but has been much exaggerated — as a big review of 372 studies has concluded. One recent experiment with a common Caribbean coral found that rising carbon dioxide levels would have no impact on its ability to build reefs for several centuries, while modest warming would actually help it slightly.

With tens of thousands of activists and bureaucrats heading for a UN conference in Paris next month, there is such vast vested interest now in demonising carbon dioxide that it will be hard to change the world’s mind. Freeman Dyson laments that “scientific colleagues who believe the prevailing dogma about carbon dioxide will not find Goklany’s evidence convincing”, but hopes that a few will try. Amen.

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