Abstract
The contributions of single greenhouse gas emitters to country-level climate change are generally not disentangled, despite their relevance for climate policy and litigation. Here, we quantify the contributions of the five largest emitters (China, US, EU-27, India, and Russia) to projected 2030 country-level warming and extreme hot years with respect to pre-industrial climate using an innovative suite of Earth System Model emulators. We find that under current pledges, their cumulated 1991–2030 emissions are expected to result in extreme hot years every second year by 2030 in twice as many countries (92%) as without their influence (46%). If all world nations shared the same fossil CO2 per capita emissions as projected for the US from 2016–2030, global warming in 2030 would be 0.4 °C higher than under actual current pledges, and 75% of all countries would exceed 2 °C of regional warming instead of 11%. Our results highlight the responsibility of individual emitters in driving regional climate change and provide additional angles for the climate policy discourse.
Highlights
The contributions of single greenhouse gas emitters to country-level climate change are generally not disentangled, despite their relevance for climate policy and litigation
The focus is set on the contributions of the top five largest emitters— China, the United States (US), the European Union (EU-27), India, and Russia—to country-level warming and extreme hot years with respect to pre-industrial climate (1850–1900) over two time periods: (1) the time period during which policy-makers have been informed about the looming climate crisis by the Intergovernmental Panel on Climate Change (IPCC) (1991–2030, the IPCC period), and (2) the time period after the Paris Agreement was reached (2016–2030, the Paris period)
The increase throughout the IPCC period is mostly caused by the top five emitters, who are set to be responsible for 52% of the total emissions during the IPCC period and 53% during the Paris period under currently pledged Nationally Determined Contributions (NDCs)
Summary
The contributions of single greenhouse gas emitters to country-level climate change are generally not disentangled, despite their relevance for climate policy and litigation. Our results highlight the responsibility of individual emitters in driving regional climate change and provide additional angles for the climate policy discourse It has been known for over a century that human-induced greenhouse gas (GHG) emissions lead to a warming planet[1,2,3]. Recent studies have highlighted the relevance of assigning climate change responsibility to major emitters[9,10,11,12,13,14,15], in order to better quantify the contributions of individual countries to human-induced global warming and its consequences This has gained importance with the bottom-up approach to mitigation that was introduced as part of the Paris Agreement, in which each country decides its own mitigation efforts without international negotiations. The precise scientific framing—e.g., regarding considered time periods, GHGs, and emission allocations—strongly influences the obtained relative contributions of individual emitters to the overall warming[10,11]
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