As much as one-third of the world's population will be exposed to Sahara
Desert-like heat within half a century if greenhouse gas emissions continue to
rise at the pace of recent years. Scientists from China, the US and Europe found
that the narrow climate niche that has supported human society would shift more
over the next 50 years than it had in the preceding 6000 years.
As many as 3.5 billion people will be exposed to near-unliveable temperatures
averaging 29 degrees through the year by 2070. Less than 1 per cent of the
Earth's surface now endures such heat.
That heat compares with the narrow 11- to 15-degree range that has supported
civilisation over the past six millennia, according to research published
Tuesday in the journal Proceedings of the National Academy of Sciences.
Absent climate mitigation or migration, a substantial part of humanity will be
exposed to mean annual temperatures warmer than nearly anywhere today, the paper
Xu Chi, a researcher at China's Nanjing University and one of the paper's
We were frankly blown away by our own initial results. As our findings were
so striking, we took an extra year to carefully check all assumptions and
Clearly we will need a global approach to safeguard our children against the
potentially enormous social tensions the projected change could invoke.
Among the most exposed nations will be India - where many people live in
already-hot places - with as many as 1.2 billion people likely to be forced to
move if population and warming trends continue. For Nigeria, the number exposed
could be 485 million, according to a media release distributed along with the
The scenario used projected the total populations in India and Nigeria to reach
2.2 billion and 600 million, respectively, by 2070, Dr Xu told
the Herald and The Age.
In Australia, areas of Western Australia and the Northern Territory home to
about 200,000 people will be at risk.
The research extended current population and greenhouse gas emissions trends
into the future, and excluded impacts from the coronavirus pandemic on both.
The researchers also considered possible rainfall changed. The global pattern of
population distribution seems less constrained by precipitation - while there is
also an optimum around 1000 mm [of rainfall a year ] - so we focused on
temperature, Dr Xu said. Changes of precipitation regime would definitely have
impacts, but such impacts together those of temperature change would be more
complex to foresee.
Compared with pre-industrial-era conditions, temperatures globally will be about
3 degrees hotter by 2070. But as land warms faster than the oceans, the rise for
people on average will be about 7.5 degrees, the paper found.
Should the world adopt strong emissions reductions - the so-called
Representative Concentration Pathway 2.6 - it would substantially reduce the
geographical shift in the niche of humans and would reduce the theoretically
needed movement to about 1.5 billion people, the paper said.
Still, that number would account for about one in seven of the world's
Each degree of temperature rise above the current baseline roughly corresponds
to 1 billion humans left outside the temperature niche, absent migration, it
The researchers added that upheavals among populations - and the ecosystems that
support them - could happen well before 2070. Migration inevitably causes
tension, even now, when a relatively modest number of about 250 million people
live outside their countries of birth.
Tim Lenton, director of the Global Systems Institute at the University of Exeter
and one of the paper's authors, said: The good news is that these impacts can be
greatly reduced if humanity succeeds in curbing global warming.
Marten Scheffer, a professor at Wageningen University and an author of the
report, said the response to the coronavirus should give cause for some optimism
that climate change's looming threats could also be tackled.
The COVID-19 response revealed that if a problem appears to be urgent and
serious, humanity globally is able to act massively if needed, even if there are
economic costs, he told the Herald and The Age. Perhaps this may serve to make
it feel more doable to address global warming too. Our findings indicate that
that would be worthwhile.