AVERTING the worst consequences of human-induced climate change is a “great moral issue” on a par with slavery, according to the leading Nasa climate scientist Prof Jim Hansen.

He argues that storing up expensive and destructive consequences for society in future is an “injustice of one generation to others”.

Hansen, who will on Tuesday be awarded the prestigious Edinburgh Medal for his contribution to science, will also in his acceptance speech call for a worldwide tax on all carbon emissions.

In his lecture, Hansen will argue that the challenge facing future generations from climate change is so urgent that a flat-rate global tax is needed to force immediate cuts in fossil fuel use. Ahead of receiving the award — which has previously been given to Sir David Attenborough, the ecologist James Lovelock, and the economist Amartya Sen — Hansen said that the latest climate models had shown the planet was on the brink of an emergency. He said humanity faces repeated natural disasters from extreme weather events which would affect large areas of the planet.

“The situation we’re creating for young people and future generations is that we’re handing them a climate system which is potentially out of their control,” he said. “We’re in an emergency: you can see what’s on the horizon over the next few decades with the effects it will have on ecosystems, sea level and species extinction.”

Now 70, Hansen is regarded as one of the most influential figures in climate science; the creator of one of the first global climate models, his pioneering role in warning about global warming is frequently cited by climate campaigners such as former US vice president Al Gore and in earlier science prizes, including the $1m Dan David prize. He has been arrested more than once for his role in protests against coal energy.

Hansen will argue in his lecture that current generations have an overriding moral duty to their children and grandchildren to take immediate action. Describing this as an issue of inter-generational justice on a par with ending slavery, Hansen said: “Our parents didn’t know that they were causing a problem for future generations but we can only pretend we don’t know because the science is now crystal clear.

“We understand the carbon cycle: the CO2 we put in the air will stay in surface reservoirs and won’t go back into the solid earth for millennia. What the Earth’s history tells us is that there’s a limit on how much we can put in the air without guaranteeing disastrous consequences for future generations. We cannot pretend that we did not know.”

Hansen said his proposal for a global carbon tax was based on the latest analysis of CO2 levels in the atmosphere and their impact on global temperatures and weather patterns. He has co-authored a scientific paper with 17 other experts, including climate scientists, biologists and economists, which calls for an immediate six per cent annual cut in CO2 emissions, and a substantial growth in global forest cover, to avoid catastrophic climate change by the end of the century.

The paper, which has passed peer review and is in the final stages of publication by the US journal Proceedings of the National Academy of Sciences, argues that a global levy on fossil fuels is the strongest tool for forcing energy firms and consumers to switch quickly to zero carbon and green energy sources. In larger countries, that would include nuclear power.— The Guardian, London