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Modeling of emissions: the earth could warm up by 2.9 degrees by 2100

2021-11-22T16:04:42.102Z


Researchers have calculated the most likely course of greenhouse gas emissions by the end of the century, based on today's climate policy. A temperature rise of less than two degrees is almost impossible.


Enlarge image

Industrial chimney: In order to limit global warming to less than two degrees, the emission of greenhouse gases would have to be reduced significantly.

Photo: Martin Schroeder / imago images / CHROMORANGE

The 2-degree target, which the world community agreed on in the Paris Climate Agreement, hardly seems to be attainable.

This is the result of a study that was published in the journal "Nature Climate Change".

For this study, a new method was used to model the development of greenhouse gas emissions up to the year 2100.

Seven scenarios were determined for the increase in greenhouse gas emissions - none of which is encouraging: Depending on the various assumptions used in the respective model, the calculations result in a forecast for an average global warming of 2.2 to 2.9 degrees by 2100 compared to pre-industrial times.

Seven models, little hope

According to the authors of the study, earlier models were mostly based on a set temperature target - for example the 2-degree target. For this purpose, certain emission profiles have been assumed that are compatible with this goal. For the new study, on the other hand, the most likely course of emissions up to 2100 was calculated based on the climate policy implemented today: the scientists compared seven models with which the development of the energy industry and society over the next few decades could be determined.

Each of these models work with different assumptions - for example, how quickly the expansion of renewable energies will proceed, what proportion of hydrogen can achieve in the energy mix, or to what extent it will be possible to extract CO₂ from the atmosphere and store it in the ground. But population growth in individual regions also plays a role. The members of the research team combined these assumptions with a number of scenarios of how climate policy measures could develop worldwide by 2030 and beyond.

Some of the scenarios identified were based solely on data on current regional climate policies. Others also assumed that all states will meet their national climate targets by 2030. Long-term net zero promises - such as those made by China, which wants to become climate-neutral by 2060, or India, which wants to reach the mark by 2070 - were not taken into account by the authors.

Oliver Geden from the Science and Politics Foundation described this approach as "very useful": This avoids the mistake of "rewarding" the global community for long-term announcements. "All net-zero targets for the middle of the century are basically promises, the probability of which cannot yet be made reliable estimates," said the climate expert and lead author of the IPCC's current status report. In the case of some of these national neutrality targets, for example in the case of India, it is also unclear whether they relate only to CO₂ or to all greenhouse gases - "the latter would be much more demanding, especially in countries like India, in which agriculture plays a major role." , so Geden.

Even the most optimistic model predicts a warming of more than two degrees

What the study also shows: The choice of model has a major influence on the temperature increase at the end of the modeling.

The researchers emphasized that it is hardly possible to compress the degree of global warming to a single number - the uncertainty associated with the respective models is too great.

But: Even with the most optimistic modeling, global warming will rise to over two degrees by 2100.

It plays a subordinate role here whether or not countries fully meet their climate targets by 2030.

The data that are evaluated in the study come from September 2021. The most recent commitments made at the UN climate conference in Glasgow are not taken into account.

Reports and calculations published during and after the climate conference are broadly in line with the results of the new study.

Based on the current climate policy, an average global warming of around 2.7 degrees compared to the pre-industrial level can be assumed.

Only if all states keep their promises of climate neutrality - which, according to a report by the Climate Action Tracker, must be considered highly questionable - can warming to around 1.8 degrees by 2100 be expected.

"All of these scenarios are possible," said Klaus Hubacek from the University of Groningen.

They depend on the political choices we make.

Given the decisions we are currently making - for example, to continue subsidizing fossil fuels and investing in infrastructure and fossil fuel extraction - we seem to be moving towards the upper end of the model scenarios. "

Do we have to give up the 2 degree goal?

However, this does not have to mean that the world has to give up the 2-degree goal: "According to the current state of research, the 2-degree goal can still be achieved," says Geden.

Not because the climate policy turned out to be particularly ambitious, but because the remaining CO₂ budget had been revised upwards: In the fifth assessment report, the remaining budget from 2011 was 1000 gigatons, in the sixth assessment report the amount of CO₂ that was emitted can be estimated at 1150 gigatons from 2020 before the climate target is exceeded.

If you take into account the real emissions between 2011 and 2019, so Give, the difference is around 500 gigatons.

more on the subject

Climate researcher Johan Rockström on the World Climate Conference: "We are on the way to a dangerous future" An interview by Susanne Götze

Alexander Nauels, who works for the NGO Climate Analytics, explained the different forecasts up to the end of the century as follows: »A three-way division is to be made: Current measures lead to a forecast of around 2.7 degrees warming in 2100. The emission reduction commitments for 2030 lead to one Forecast of around 2.4 degrees warming in 2100. The 2030 emission reduction commitments plus vague net-zero promises lead to a forecast of around 1.8 degrees warming in 2100. "How far global warming can be limited - and whether even the 1st The 5-degree target can be met is a question of political will, said Nauels.

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Source: spiegel

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