世界の気温、１０年で過去最高の０．２度上昇　論文で警鐘

【パリＡＦＰ＝時事】世界の著名な科学者５０人は８日、温室効果ガスの排出量が過去最多に上ったことと太陽光を遮る大気中の汚染物質が減少したことにより、地球温暖化が前例のないペースで進行していると警鐘を鳴らした。（写真はイラク南部チバイッシュ湿原で、干上がったの地面を歩く少年〈資料写真〉）
　政策立案者向けにまとめられた査読済みの論文が、学術誌「地球システム科学データ」に掲載された。論文では、２０１３年～２２年の１０年間に気温上昇の幅は０．２度を上回り、「人間の活動に起因する」温暖化がこれまでにないペースで進行していることが報告された。
　一方で論文は、この１０年で最も成功した気候変動対策の一つである石炭の使用量削減により、皮肉にも温暖化のペースが加速したと指摘している。
　石炭の使用量削減により、二酸化炭素（ＣＯ２）の排出量は抑制することができたが、これによって、太陽光を遮っていた大気汚染も減少した。
　大気汚染によるあらゆる微粒子によって、温度上昇は０．５度抑制される。つまり少なくとも短期的には、空気が浄化されるにつれて、より多くの太陽エネルギーが地表に到達することになる。
　今回の研究結果は、世界の気温上昇を産業革命前と比べて１．５度に抑える「パリ協定」の目標達成に投げ掛けるものとなった。【翻訳編集ＡＦＰＢＢＮｅｗｓ】
〔ＡＦＰ＝時事〕（2023/06/09-16:33）

Record-high greenhouse gas emissions and diminishing air pollution have caused an unparalleled acceleration in global warming, 50 top scientists warned Thursday in a sweeping climate science update.
From 2013 to 2022, human-induced warming has been increasing at an unprecedented rate of over 0.2 degrees Celsius per decade, they reported in a peer-reviewed study aimed at policymakers.
Average annual emissions over the same period hit an all-time high of 54 billion tonnes of CO2 or its equivalent in other gases -- about 1,700 tonnes every second.
World leaders will be confronted with the new data at the critical COP28 climate summit later this year in Dubai, where a Global Stocktake at the UN talks will assess progress toward the 2015 Paris Agreement's temperature goals.
The findings would appear to close the door on capping global warming under the Paris treaty's more ambitious 1.5C target, long identified as a guard rail for a relatively climate-safe world, albeit one still roiled by severe impacts.
Even though we are not yet at 1.5C warming, the carbon budget -- the amount of greenhouse gases humanity can emit without exceeding that limit -- will likely be exhausted in only a few years, said lead author Piers Forster, a physics professor at the University of Leeds.
That budget has shrunk by half since the UN's climate science advisory body, the Intergovernmental Panel on Climate Change (IPCC), gathered data for its most recent benchmark report in 2021, according to the Forster and colleagues, many of whom were core IPCC contributors.
- Unintended consequences -
To have even a coin-toss chance of staying under the 1.5C threshold, emissions of carbon dioxide, methane and other drivers of warming generated mostly by burning fossil fuels must not exceed 250 billion tonnes (Gt), they reported.
Bettering the odds to two-thirds or four-fifths would reduce that carbon allowance to only 150 Gt and 100 Gt, respectively -- a two- or three-year lifeline at the current rate of emissions.
Keeping the Paris temperature targets in play would require slashing CO2 pollution at least 40 percent by 2030, and eliminating it entirely by mid-century, the IPCC has calculated.
Ironically, one of the big climate success stories of the last decade has inadvertently hastened the pace of global warming, the new data reveal.
A gradual drop in the use of coal -- significantly more carbon intensive than oil or gas -- to produce power has slowed the increase in carbon emissions.
But it has also reduced the air pollution that shields Earth from the full force of the Sun's rays.
Particle pollution from all sources dampens warming by about half-a-degree Celsius, which means -- at least in the short term -- more of that heat will reach the planet's surface as the air becomes cleaner.
Published in the peer-reviewed journal Earth System Science Data, the new study is the first in a series of periodic assessments that will help fill the gaps between IPCC reports, released on average every six years since 1988.
- Deadly heat -
An annual update of key indicators of global change is critical in helping the international community and countries to keep the urgency of addressing the climate change crisis at the top of the agenda, said co-author and scientist Maisa Rojas Corradi, who is also the environment minister of Chile.
Co-author Valerie Masson-Delmotte, a co-chair of the 2021 IPCC report, said the new data should be a wake-up call ahead of the COP28 summit, even if there is evidence that the increase in greenhouse gases has slowed.
The pace and scale of climate action is not sufficient to limit the escalation of climate related risks, she said.
Researchers also reported a startling rise in temperature increases over land areas -- excluding oceans -- since 2000.
Land average annual maximum temperatures have warmed by more than half a degree Celsius in the last ten years (1.72C above preindustrial conditions) compared to the first decade of the millennium (1.22C), the study reported.
Longer and more intense heat waves will pose a life-and-death threat in the coming decades across large swathes of South and Southeast Asia, along with areas straddling the equator in Africa and Latin America, recent research has shown.