[**Prawdopodobieństwo osiągnięcia klimatycznego celu porozumienia pary... (@Fake_R)

Prawdopodobieństwo osiągnięcia klimatycznego celu porozumienia paryskiego to zaledwie 5%.

Opis ze znaleziska:

Bazując na obecnym trendzie w redukowaniu emisji CO2 badacze przeprowadzili analizę dotrzymania zobowiązań klimatycznych porozumienia paryskiego, które zakłada utrzymanie ocieplania się klimatu na Ziemi na poziomie <2°C do 2100 r. Prawdopodobieństwo osiągnięcia tego celu to zaledwie 5%.

Krótki komentarz:

Kluczowe założenie porozumienia paryskiego wydaje się, przynajmniej na dzisiaj, praktycznie nieosiągalne - co jest niepokojącym wnioskiem.

We first address the question, what is the probability that each country will meet its NDC, given current trends? This probability is shown in Fig. 312. Given current trends, the probabilities are low for most of the major emitters, such as the USA (2%), China (16%) and Japan (10%), Germany (13%) and France (2%). For a few countries, however, such as Russia (93%), they are much higher.

Poniżej ciekawa grafika opisująca to o czym mowa w powyższym akapicie dla poszczególnych państw i ukazująca prawdopodobieństwo osiągnięcia postawionych przez państwa "celów redukcyjnych" tzw. INDC (Intended National Determined Contributions):

https://www.nature.com/articles/s43247-021-00097-8/figures/3

Przy założeniu, że stawiane przed państwami cele klimatyczne będą osiągane oraz kontynuowany będzie trend redukcyjny przedział wzrostu temperatur będzie na poziomie 1.8 - 2.9 °C - co daje wzrost rzędu 2.3°C. Prawdopodobieństwo wzrostu mniejszego niż 2°C jest jednak szacowana na zaledwie 5%.

We find that on current trends, but without additional efforts to meet the NDCs, the median forecast of global mean temperature increase is 2.8°C, with likely range (90% prediction interval) [2.1, 3.9]°C. If all countries meet their NDCs, but revert to current trends thereafter, the median forecast declines by 0.2°C to 2.6°C, with likely range [2.0, 3.4]°C. If all countries meet their NDCs and continue to reduce carbon emissions at the same rate thereafter, the median forecast declines by a further 0.3°C, to 2.3°C, with likely range [1.8, 2.9]°C. The probability of staying below 2°C is 5% under the “None” scenario, 12% under the “Ajusted” scenario, and 26% under the “Continued” scenario.

Our results suggest that even if all countries meet their promises under the Paris Agreement and continue to reduce emissions at the same rate thereafter, it is unlikely that warming would stay under 2°C, a conclusion also reached by other authors using different approaches

Oczywiście, chcąc zatrzymać wzrost na poziomie poniżej 2°C do końca stulecia konieczne musi być dążenie do radykalnego ograniczenia emisji CO2 - najlepiej do połowy wieku osiągnąć zerowe emisje netto, aczkolwiek autorzy badania zauważają, że niekoniecznie musi być to całkowite ich ograniczenie globalnie przed 2100 r. Niemniej sugerują również, że w przeciwieństwie do raportów IPCC redukcja emisji do 2030 r. powinna być na poziomie 80% w przeciwieństwie do 45% z badań IPCC.

Note that to have an even chance of limiting global warming to 2°C would require global progress towards net zero fossil fuels and industry emissions, but it would not require global annual emissions to reach net zero before 2100, although it would likely involve individual countries doing so. Under this scenario, emissions would need to decline by about 80% relative to their median forecast in the absence of additional efforts (which is roughly equal to the current level), giving global annual emissions of about 7.8Gt CO2 by 2100.

The 2018 IPCC report on mitigation pathways compatible with staying below 1.5°C has also addressed the question of how this can be done19. They used the same general framework as the IPCC 2014 AR5 report3, basing results on scenarios for future socioeconomic and energy intensity outcomes, combined with ensembles of climate models to translate these into climate outcomes, rather than the fully statistical probabilistic framework we use here. Nevertheless, our results are broadly in line with theirs, albeit with some differences.

They conclude, as do we, that even if the NDCs are met and mitigation continues after 2030, global warming is likely to surpass 1.5°C. They argue that to stay below 2°C in 2100 with probability 66% would require that total GHG emissions decline by 25% from 2010 to 2030, while our method suggests that a reduction of 31% in fossil fuels and industry CO2 would be required to achieve the same goal with probability 50%. The interpretations of probability are different, as theirs are based on ensembles of scenarios and our method produces calibrated probability distributions, but the results are similar. They also conclude that to achieve this would require net zero emissions by 2070. Our method suggests that it would require a 66% reduction in emissions from 2010 to 2070, and that this goal could be achieved without reaching net zero globally. This would, however, require sustained emissions reduction throughout the century, and would require close to net zero emissions to be reached in many countries to achieve the large global total emissions reductions needed.

They conclude that to stay below 1.5°C would require a 45% reduction in emissions from 2010 to 2030, reaching net zero emissions globally by 2050. Our method suggests that this would require an even larger reduction of around 80%, reaching close to net zero emissions by 2045. Again, the results are qualitatively similar.