It?s a law of physics that translates well into the behaviour of human beings : the greater the mass involved, the more effort is needed to overcome its inertia. But it doesn?t read very well as an epitaph for civilisation.

The information we need in order to act is around us every day. Three small, low-key stories in the inner pages of the newspapers I read at breakfast -- the sort of stories you find in the media almost every day -- should have been enough to galvanise every reader into instant action. But the human version of the laws of physics gets in the way.

The first story was a warning by the Meteorological Office in Britain that summer temperatures in south-eastern England may reach as high as 46 degrees C by the end of this century. "By 2100, such heatwaves are likely to occur almost every year, and could occur several times in any given summer," said the Met Office.

London with the summer temperatures similar to Kuwait?s seems incredible, but the Met Office was relentlessly reasonable. Depending on how fast greenhouse gas emissions rise, it pointed out, we are facing an average rise in global temperature rise of between two and five degrees Celsius by the end of this century.

If the atmospheric concentration of carbon dioxide is halted at the level of 450 parts per million, then we get away with "only" two degrees hotter. But we are already at 385 ppm, so that requires immediate global agreement on radical action to curb the growth of CO2 emissions. Allow the current model of economic development and energy use to continue basically unchanged, and you end up with 800 ppm by the end of the century and the five degrees hotter world.

The second story was about a "green growth plus" strategy devised by consultants at Pricewaterhou-seCoopers, the US-based giant that provides a wide range of business services including risk management. Basically, the report said that it wouldn?t cost all that much to save civilisation.

The economists at Pricewater-houseCoopers calculated that serious efforts to improve energy efficiency, greater use of renewable energy, and new technologies for carbon capture could cut global CO2 emissions by about 60 percent from the level predicted for 2050 if countries just pursue a "business-as-usual approach." Moreover, the costs involved would not beggar us all.

"Estimates suggest that the level of (world Gross Domestic Product) might be reduced by no more than two to three percent by 2050 if this strategy is followed," said John Hawksworth, head of macro-economics at PwC. But the success of the strategy does depend on getting really serious about global heating RIGHT NOW.

Is that really likely to happen ?

The third story seemed encouraging at first, for it reported that scientists now believe the battle to close the "ozone hole" is being won.

It is an impressive tale of global cooperation to stop human activities that damage vital natural systems. The ozone hole was first spotted in 1985, and soon researchers linked it conclusively with chlorofluorocabons, compounds that were widely use in refrigerators, air-conditioners and aerosol sprays.

However, the Montreal Protocol of 1987 restricted the production of CFCs only two years after the hole was discovered. The Antarctic hole still covered an area bigger than all of North America this month, but scientists are now confident that the worst is past. It will stay at about this size for fifteen or twenty years, and then "somewhere between 2020 and 2025 we?ll be able to detect that the ozone hole is actually beginning to decrease in size," said Paul Newman of NASA?s Goddard Space Flight Center in Maryland. Within seventy years, the hole should be entirely healed So why can?t we react as fast to global warming ? Because of inertia : the mass of people and institutions to be moved is just so great.

Fixing the ozone hole was easy because neither hair-spray nor refrigerator coolants are centrally important in the economy. Changing the way we produce and use energy is not easy at all, even if PricewaterhouseCoopers are right and the ultimate level of economic sacrifice would not be that great. So many people and institutions are involved that it?s hard to move fast, even if failing to do so costs us the Earth.