Butterfly futures flutter by

James Hansen’s latest discussion paper begins and ends with Monarch butterflies. He watches some on his property in Pennsylvania as they prepare to leave for their migration to Mexico and reflects on the prospects for their survival as a species as global warming takes hold. The Monarchs cross Texas on their way south, a difficult path this year over desolate, baked-out territory. Which leads Hansen to a spirited denunciation of “well-oiled Governors and Senators in Texas and Oklahoma” who assert that global warming is a hoax and help business-as-usual CO₂ emissions to continue.

He addresses the question of whether the drought and fires in Texas can be attributed to global warming. The media have remained largely silent this year on possible connections between extreme weather events and human-made climate forcing, and Hansen asks whether scientists should be making more effort to draw public attention to the human role in climate anomalies.

The longstanding difficulty in such communication is distinguishing climate change caused by global warming from natural climate variability.  “The human-made climate ‘signal’ must be extracted from the large ‘noise’.” But he thinks the public can understand the distinctions.

He sets out the reasons we can expect intensified climate extremes from global warming:

(1) Warmer air holds more water vapor, and precipitation occurs in more extreme events. ‘100-year floods’ and even ‘500-year floods’ will become more likely. Storms fueled by water vapor (latent heat), including thunderstorms, tornadoes and tropical storms, will have the potential to be stronger. Storm damage will increase because of increased flooding and stronger winds.

(2) Where weather patterns create dry conditions, global warming will intensify the drought, because of increased evaporation and evapotranspiration. Thus fires will be more frequent and burn hotter. Observations confirm that heat waves and regional drought have become more frequent and intense over the past 50 years. Rainfall in the heaviest downpours has increased about 20 percent. The destructive energy in hurricanes has increased (USGCRP, 2009).

What about the Texas drought? Is it related to human-made global warming?

There is strong reason to believe that it is. Basic theory and models (Held and Soden, 2006) and empirical evidence (Seidal and Randel, 2006) indicate that the global overturning circulation, air rising in the tropics and subsiding in the subtropics, expands in latitude with global warming. Such expansion tends to make droughts more frequent and severe in the southern United States and the Mediterranean region, for example.

But while the occurrence of unusual Texas heat and drought is consistent with expectations for increasing CO2, may this year’s event just be climate ‘noise’?

I used ‘climate dice’ in conjunction with testimony to Congress in 1988 to try to help the public understand that the human-made climate ‘signal’ must be extracted from the large ‘noise’ of natural climate variability.

In an upcoming post (Climate Variability and Climate Change, Hansen, Sato and Ruedy) we try to clarify this matter via simple maps and graphs that show how the odds have changed, allowing comparison of expectations and reality…

We show that a ‘signal’ due to global warming is already rising out of the climate ‘noise’, even on regional scales.

Hansen offers maps and some technical detail to illustrate this, and concludes:

The chaotic element in climate variability makes it impossible to say exactly where large anomalies will occur in a given year. However, we can say with assurance that the area and magnitude of the anomalies and their practical impact will continue to increase. Clear presentations of the data should help the public appreciate the situation as global warming continues to rise further above the level of natural variability.

So much for the longstanding difficulty for scientists in helping the public understand the distinction between climate variability and the overall trend of the effects of global warming. But Hansen also describes a new difficulty which has arisen more recently and which has nothing to do with the science. It is the character assassination of scientists, mainly directed against Ben Santer, Michael Mann and Phil Jones.

The important point I wish to note is that each of these three targets, the scientific conclusions that provoked the critics and which they aimed to destroy or discredit, have been shown in subsequent analyses to have been correct, indeed, dead-on-the-mark.

However, the scientific community is well aware of the toll that these attacks took on the scientists, despite the fact that their work was eventually vindicated and corroborated.

Thus, it would not be surprising if these experiences have an effect on the willingness of other scientists to make statements that draw attention to the likely role of human-made forcings as a contributor to the climate extremes of the past summer.

But the “inherent objectivity” of science is needed to help society find a path which will avoid our exiting the stable Holocene climate in which civilisation developed. Hansen is not prepared to stop short of engagement with the policy implications of the science, though governments want scientists to do so. He explains why:

If scientists do not connect all of the dots in this story, the dots will be connected by people with a vested interest in preserving the fossil fuel industry. The resources that the fossil fuel industry brings to bear in protecting its economic interests are formidable. The public is immersed daily in advertisements using effective spokespeople including skilled professional actors. Their message has appeal. They say that efforts to extract fossil fuels in tar sands, in the Arctic, and so on, would provide jobs and produce needed energy.

Existing irrefragable climate science makes clear that this path – advocated by the fossil fuel industry and supported by governments worldwide – would be calamitous for young people and nature. Yet if scientists bring only this negative message, there is no hope of stopping the fossil fuel juggernaut with its aim to exploit all fossil fuels.

Hansen’s positive message, which is well known by now, is that the way forward is a rising carbon fee or tax collected from fossil fuel companies and returned to the population on a per capita basis. He has been criticised for his advocacy of a fee-and-dividend policy and blunt rejection of cap-and-trade schemes, which he describes in this paper as “designed to allow business-as-usual, leading to certain mining of all fossil fuels on the planet and a debacle for young people”.

His specific advocacy may be arguable. However it is important that scientists who know the consequences of continuing to extract and burn fossil fuels should speak up if politicians who claim to be addressing the problem are at the same time allowing and even abetting the further exploitation of fossil fuels – as if the magic of trading and offsetting will somehow render them harmless. That appears to be very much the case in New Zealand under present government policies which unashamedly look to a prosperous future from fossil fuel exploration and exploitation while running an ineffectual ETS on the side and getting credit internationally for doing so. Hansen’s forthrightness exposes this for the greenwash that it is.

And his carbon tax proposals are not foolish, even if they’re not flavour of the month.  I recently reviewed Shi-ling Hsu’s book The Case for A Carbon Tax, which advanced a strong and well-considered argument for such an approach. Al Gore has expressed his preference for a carbon tax albeit acknowledging it is not currently acceptable in the US.

Hansen’s paper ends wryly with those butterflies:

Survival of the Monarch will depend more on conditions in Mexico than in Texas. If business-as-usual continues and we burn most of the fossil fuels this century, it is unlikely that those forests [where the Monarchs winter] or the Monarchs will survive. There is not much that the Monarch can do about this matter. Their fate will be up to the intelligent species.