Explanation: The five futures of the UN climate report – decoded

Aug. 9 (Reuters) – The UN climate panel report released on Monday on the physical science of climate change uses five possible scenarios for the future. Read more

Scenarios are the result of complex calculations that depend on how quickly humans reduce greenhouse gas emissions. But the calculations also aim to capture socio-economic changes in areas such as population, urban density, education, land use and wealth. Read more

For example, an increase in population is believed to lead to an increase in demand for fossil fuels and water. Education can influence the pace of technological developments. Emissions increase when land is converted from forests to agricultural land.

Each scenario is labeled to identify both the level of emissions and the shared socio-economic pathway, or SSP, used in these calculations.

Here’s how to understand each:

FIVE FUTURES – DECODED

SSP1-1.9: The IPCC’s most optimistic scenario, it describes a world where global CO2 emissions are reduced to net zero by 2050. Societies are shifting to more sustainable practices, the focus shifting from economic growth to good. be general. Investments in education and health are increasing. Inequality falls. Extreme weather conditions are more common, but the world has dodged the worst impacts of climate change.

This first scenario is the only one that meets the Paris Agreement goal of keeping global warming at around 1.5 ° C above pre-industrial temperatures, with warming reaching 1.5 ° C, then falling and continuing. stabilizing around 1.4 ° C by the end of the century.

SSP1-2.6: In the next best-case scenario, global CO2 emissions are reduced severely, but not as rapidly, reaching net zero after 2050. He imagines the same socio-economic changes towards sustainability as SSP1-1.9. But temperatures will stabilize around 1.8 ° C higher by the end of the century.

SSP2-4.5: This is a “halfway” scenario. CO2 emissions hover around current levels before starting to decline in mid-century, but do not reach net zero by 2100. Socio-economic factors follow their historical trends, without noticeable changes. Progress towards sustainability is slow, with development and incomes increasing unevenly. In this scenario, temperatures increase by 2.7 ° C by the end of the century.

SSP3-7.0: On this path, emissions and temperatures rise steadily, and CO2 emissions roughly double from current levels by 2100. Countries become more competitive with each other, moving towards safety national level and ensuring their own food supplies. At the end of the century, average temperatures had risen by 3.6 ° C.

SSP5-8.5: It’s a future to be avoided at all costs. Current levels of CO2 emissions will roughly double by 2050. The global economy is growing rapidly, but this growth is fueled by the exploitation of fossil fuels and energy-intensive lifestyles. By 2100, the average global temperature is 4.4 ° C higher.

WHAT DO WE LEARN FROM THEM?

The climate report cannot tell us which scenario is more likely – which will be decided by factors, including government policies. But it shows how today’s choices will affect the future.

In all scenarios, warming will continue for at least a few decades. Sea levels will continue to rise for hundreds or thousands of years, and the Arctic will be virtually free of sea ice for at least one summer over the next 30 years.

But the speed at which the sea will rise and the dangerousness of the weather always depend on which route the world chooses to take.

Reporting by Andrea Januta; Editing by Katy Daigle and Lisa Shumaker

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