The Republican victory in the US midterm elections was a triumph for its strategy of sustained vilification of the president and obstruction of his policies. The result will have big implications for the future of the US. But it also has implications for the rest of humanity.

This is inevitable, given the role of the US as the world’s largest and most technologically advanced economy, guarantor of the open world economy and greatest military power. But the US is also the world’s second-largest emitter of greenhouse gases and among the highest emitters per head.

The most important consequence of this election may therefore be to bury what little hope remained of getting to grips with the risk of dangerous climate change. Countries can’t keep bits of the atmosphere to themselves. Moving off the world’s current trajectory is a collective task. Without US will and technological resources, the needed shift will not happen.

The climate hoax

Many Republicans seem to have concluded that man-made climate change is a hoax. If so, this is quite a hoax. Just read the synthesis report of the Intergovernmental Panel on Climate Change. One is asked to imagine that thousands of scientists have put together a complex fabrication in order to promote their not particularly remunerative careers, in the near certainty they will be found out. This hypothesis makes no sense.

What, then, are some of the main points to take away from this report?

It starts with where we now are. Warming of the climate system is “unequivocal”. Atmospheric concentrations of greenhouse gases are at levels not seen in at least 800,000 years. In addition, human-caused emissions of such gases have risen consistently.

It is also “extremely likely” that more than half the observed increase in global average surface temperature from 1951 to 2010 is due to human activity.

If we continue on our path, the report adds, larger changes in climate are highly likely. The equilibrium rise in global average surface temperatures caused by a doubling of carbon dioxide concentrations relative to pre-industrial levels would be between 1.5C and 4.5C. But the concentrations of greenhouse gases have already risen by more than 40 per cent.

Likely consequences of further rises include disease, extreme weather, food and water insecurity, and loss of biodiversity and ecosystems.

The report also argues that mitigation of emissions and adaptation to their effects are complementary strategies, not substitutes: we need to do both. On the cost of mitigation, it argues that efficient policies likely to limit warming to below 2C relative to pre-industrial levels entail losses in global consumption of 1 to 4 per cent in 2030 and 3 to 11 per cent in 2100.

The philosophical and practical challenges are huge. But we must remember that neither emissions nor the climate consequences can be reversed: melted glaciers are gone indefinitely. Moreover, the longer we wait, the more we will have to do if we are to limit the impact.

Nothing now suggests that humanity will move off the path towards ever greater emissions, with potentially irreversible consequence. Why is that? If one ignores the charge that the science is a hoax, one sees two justifications and two reasons.

Cost of no action

One justification is that cost of action to mitigate emissions would be inordinate. It should be noted, however, that the costs indicated above would be less, possibly substantially less, than the costs to the high-income countries of the recent financial crises. These have lowered gross domestic product by around a sixth, relative to pre-crisis trends, in the US, UK and euro zone.

In some economies, when the losses are counted, they will be far bigger. Moreover, it seems likely that these losses will never be recouped.

Yet, fascinatingly, the very same people who consider the costs of mitigation excessive wish to lighten financial regulation and so increase the risk of a repetition of the recent calamity. In addition, many of the opponents of such action are firm believers in the ability of economies to respond to market forces. So why do they not believe that markets would adjust to higher carbon prices?

Another justification is the uncertainty. Uncertainty is indeed rife, as the IPCC makes clear. But one must not confuse the uncertainty of outcomes with the certainty of no outcomes. These are two quite distinct propositions.

Russian roulette

What would you feel if someone justified his decision to overtake on corners with the argument that one could not be certain a car was coming in the opposite direction? You would think he was playing Russian roulette. Why would anybody think that makes sense in dealing with the only habitable planet we know of? Under uncertainty, the rational path is to insure against extreme outcomes.

So what, then, are the real reasons? The first is ideology. If one accepts the existence of large global environmental externalities, one must also accept that there exists an important role for policy in shaping market outcomes. It is no accident that believers in laissez-faire are the fiercest climate sceptics. The wish is father to the denial.

The second and more important reason is indifference to the fate of future generations. Why should we bear costs of mitigation today for the benefit of those we will never know, even if that includes our own descendants? After all, the indifferent might ask, what have future generations ever done for us?

The ethical response is that we are the beneficiaries of the efforts of our ancestors to leave a better world than the one they inherited. We have the same obligation even if, in this case, the challenge is so complex. But, however strong such a moral argument may be, it is most unlikely to overcome the inertia we now see.

Future generations, and even many of today’s young, might curse our indifference. But we do not care, do we? – Copyright 2014 The Financial Times Limited