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We must come up with ways to buy more time in the battle against Climate Change, writes Jim Flynn.

Virtually everyone now concedes that there is significant global warming and that carbon emissions play at least some role.

Young people in particular are agitating for steps to reduce emissions. They point to the melting of the huge Polar Glaciers as alarming, but they do not see that this is a game-changer and means that they must add to their message.

Polar ice has always acted as a gigantic mirror that reflects sunlight back into space. Its erosion creates a feedback loop — less ice, higher temperature, even less ice, even higher temperature — that acts as a cause independently of the level of CO2. In other words, even if we greatly reduce carbon emissions, the ice loop may spin out of control and global warming up to 4 degrees by 2100 will be inevitable.

The consequences include a sea-level rise of at least three metres by 2100. The next century has been labelled the century from hell, as sea-level rise reaches a rate of over a metre a decade and coastal flooding of cities becomes everyone's problem (see Hanson, 2016, Atmos. Chem. Phys. & Friedrich, 2016, Science Advances 2).

Vietnam, China, and Japan will be the worst off — by 2100, China will have to spend 20% of its gross domestic product on flood damage alone.

Warming will lessen the world's supply of water and food during a period in which the UN estimates that the world's population will rise from 7.7billion (now) to 11billion (2100).

Africa's population will double much earlier, to 2.48billion by 2050. Mass starvation will ensure that this does not actually happen.

Other areas will be badly hit, Latin America from Mexico south, India, and all nations bordering on the Mediterranean including the Middle East. In Spain, 99% of its land will be less suitable for agriculture.

In Australia, which is already half desert or semi-desert, it will be 97%.

The efforts of people to leave these lands will be frantic and today's problem of discouraging refugees rendered unsolvable by anything but the machine gun.

The people of Spain, Italy, and Greece will find themselves shot at their northern borders just as they shoot anyone that comes to them by boat. The US will really close its border with Mexico. New Zealanders will not welcome millions of Australians until Australia reminds them that it has the military power to ‘‘persuade’’ them to the contrary.

Even if all this happens, the crusade to cut emissions is essential: every less degree of temperature rise will help and any carbon we can keep from dissolving in the oceans will make them less acidic, and might preserve the food chain that gives us our fish.

But it is absolutely essential to buy more time. We must lower the earth's temperature ‘‘artificially’’ long before 2050. It will probably be at least 2100 before hydrogen fusion, harnessing wind and sun and perhaps the tides, and conservation of energy can really limit carbon emissions enough.

We will just have to hope that arresting temperature rise now will allow the glaciers to recover (if they can) and stop the fatal ice loop.

Sadly this means climate engineering. My book (Flynn, 2016, second printing) tries to convince you that only one method does not have serious side effects: Salter’s proposal that we use a fleet of ships with large turbines to send up more sea spray and enhance low-lying clouds as a reflector of sun light back into space. This would mean increasing the ocean's ‘‘natural’’ spray by only 1%. But theory often fails to translate into practice.

New Zealand and other nations should go to the next climate conference and urge experimentation before it is too late: will the ships really be effective, can they encourage rainfall where we need it, will the guidance system work so we can put them in just the right positions?

Without accompanying their demand for less emissions by endorsing climate engineering, today's youth may be leading us down the road to runaway climate change.

How is that for a tragedy?

■ Jim Flynn is an author and emeritus professor of political studies at the University of Otago.