Climate change can be stopped, say scientists. Computer models show how: NPR

Electricians check the solar panels of a photovoltaic power plant built in a fish pond in Haian, east China’s Jiangsu Province.

STR / AFP via Getty Images

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STR / AFP via Getty Images

Electricians check the solar panels of a photovoltaic power plant built in a fish pond in Haian, east China’s Jiangsu Province.

STR / AFP via Getty Images

As the world’s top climate scientists this week released a report full of warnings, they kept insisting that the world still had a chance to avert the worst effects of climate change.

“It’s still possible to prevent most of the disastrous impacts, but it really requires unprecedented transformational change,” said Ko Barrett, vice-president of Intergovernmental Panel on Climate Change. “The idea that there is still a way forward, I think, is a point that should give us some hope.”

This hopeful path, in which dangerous changes in the world the climate ends up stopping, is the product of giants computer simulations of the world economy. These are called integrated assessment models. There are half a dozen major versions: four developed in Europe, one in Japan and a in the United States, at the Pacific Northwest National Laboratory.

“What we mainly do is try to explore what is necessary to achieve the Paris goals.” said Detlef van Vuuren, to the Dutch Environmental Assessment Agency, which developed one of the models.

How to reduce greenhouse gas emissions to zero in 40 years

World leaders agreed in Paris to limit global warming to less than 2 degrees Celsius (3.6 degrees Fahrenheit). The planet has already warmed by about 1 degree Celsius, compared to pre-industrial levels.

Achieving this goal will require reducing net greenhouse gas emissions to zero within about 40 years. It would require profound changes; so deep, it’s not immediately clear that it’s even possible.

That’s why van Vuuren and his colleagues turned to their computer models for help. “How to go to zero emissions?” he says. “It’s for transport, it’s for housing, it’s for electricity.”

Each of these models begins with data on current sources of greenhouse gas emissions. They include cars and buses, rickshaws, planes, power plants, domestic ovens and rice fields. The models also include assumptions about international trade, prices and costs of new technologies.

Then, scientists force their virtual worlds to change course, by introducing limits on greenhouse gas emissions. Models then attempt to meet this requirement in the most cost-effective way, as long as it is technologically feasible and does not face limitations such as the supply of land or other natural resources.

The good news is that the models found a way to achieve this, at least in scenarios where global governments were inclined to cooperate to meet their Paris commitments. Indeed, according to Keywan Riahi, at the International Institute of Applied Systems in Austria, they found multiple paths to zero carbon.

“The models tell us that there are, first of all, possible alternative paths; that there are choices available to the decision maker, ”he said.

Different models, using different assumptions, arrive at contrasting visions of the future world. But they are all radically different from where they are today.

Some models show people reacting to rising energy prices or government regulations by changing their lifestyle. They are moving to more energy efficient homes and ditching their cars in favor of a new and better type of public transportation. In addition to traditional bus lines, self-driving vehicles behave like Uber – taking people where they need to go.

Riahi prefers this version. “I am convinced that a fundamental restructuring on the demand side would also lead to a better quality of life,” he says.

Other scenarios show that people still consume a lot of energy, which in turn requires a huge increase in the production of clean electricity. This would mean 10 or 20 times more land covered by solar and wind farms, compared to now, plus more power plants burning wood or other biofuels, equipped with equipment to capture and store the carbon dioxide that is released. .

Politics and individual preferences could defeat the models

Riahi is quick to point out that what happens in models may not be achievable in real life. They ignore political obstruction, for example, or human preferences. People may just want to drive an expensive car, rather than taking public transportation, even when models say this choice is not economically rational.

But the models can also be far too pessimistic, especially when it comes to technological innovation. Ten years ago, says van Vuuren, they never anticipated the boom in cheap solar power. “We have been in the extremely fortunate position that the cost of renewables has declined rapidly over the past decade.” This has made the task of reducing carbon emissions much easier.

Despite all their shortcomings, however, these models remain the primary vehicle used by scientists and policy makers to determine options for the future. They quantify the trade-offs and consequences that may not be clearly apparent. If countries want to turn trees or crops into fuel, for example, that means less land for food crops or for natural forests. In addition, the models clearly show that international cooperation is essential, with rich countries helping poorer countries to reduce their emissions.

The results of computer modeling are like fuzzy maps, pointing to routes that could help the world avoid disasters.

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