The Paris Climate Agreement aims to limit global warming to 1.5 limits this century. A new report from the World Meteorological Organization warns that this limit could be exceeded by 2024 – and the risk is growing.
This initial overshoot beyond 1.5 ℃ would be temporary, likely aided by a major climate anomaly such as an El Niño weather pattern. However, it raises new doubts as to whether the earth’s climate can be permanently stabilized with a warming of 1.5 ° C.
This finding is among those just published in a report entitled United in science. We contributed to the report, which was produced by six leading science agencies, including the Global carbon project.
The report also found that greenhouse gas emissions decreased slightly in 2020 due to the COVID-19 pandemic, but remained very high – which meant atmospheric carbon dioxide levels continued to rise.
Greenhouse gases increase when CO₂ emissions slow down
The concentrations of the three most important greenhouse gases – carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) – have increased over the past ten years. Current concentrations in the atmosphere are 147%, 259% and 123%, respectively, of those present before the beginning of the Industrial Age in 1750.
The concentrations measured at the Mauna Loa Observatory in Hawaii and at the Australian station Cape Grim in Tasmania show that the concentrations continued to increase in 2019 and 2020. In particular, the CO₂ concentrations reached 414.38 and 410.04 ppm at each station in July this year.
The growth in CO₂ emissions from fossil fuel consumption has slowed to around one percent per year over the past ten years, after three percent in the 2000s. An unprecedented decline is expected in 2020 due to the economic slowdown from COVID-19. Daily CO₂ emissions from fossil fuels fell by 17 percent year-on-year in early April at the height of the global restriction policy. However, by early June they had rebounded to a decline of five percent.
We estimate a decrease of around four to seven percent for 2020 compared to 2019, depending on how the pandemic develops.
Although emissions will decrease slightly, atmospheric CO₂ concentrations will still be different Record high this year. This is because we are still adding large amounts of CO₂ to the atmosphere.
The warmest five years in its history
The global average surface temperature from 2016 to 2020 will be among the warmest of all recorded periods and around 0.24 ℃ warmer than in the past five years.
This five-year period is well on the way to setting new temperature records in much of the world, including Australia, southern Africa, much of Europe, the Middle East and North Asia, areas of South America and parts of the United States.
The sea level has risen by an average of 3.2 millimeters per year over the past 27 years. Growth is accelerating – sea levels have risen 4.8 millimeters annually for the past five years, compared to 4.1 millimeters a year in the previous five years.
There have also been many extreme events over the past five years. These include record-breaking heat waves in Europe, Cyclone Idai in Mozambique, major bush fires in Australia and elsewhere, prolonged drought in southern Africa and three hurricanes in the North Atlantic in 2017.
1: 4 probability of warming more than 1.5 ° C.
Our report predicts a continued warming trend. There is a high likelihood that average temperatures across the planet over the next five years will be above the 1981-2010 average. The warming of the Arctic is projected to be more than double the global average.
There is a one in four chance that the global mean annual temperature will be 1.5 ℃ above pre-industrial levels for at least a year over the next five years. The chance is relatively slim, but still significant and growing. If a major climate anomaly such as a strong El Niño occurs during this period, it is more likely that the 1.5 1.5 threshold will be exceeded. El Niño events generally bring warmer global temperatures.
According to the Paris Agreement, exceeding the 1.5 ℃ threshold is measured over a 30-year average, not just over a year. But warming above 1.5 ° C every year would bring us closer to crossing the line.
The sea ice of the Arctic Ocean is disappearing
Satellite records between 1979 and 2019 show that Arctic summer sea ice declined by about 13 percent per decade, and this year hit its lowest level since July.
In Antarctica, summer sea ice reached its lowest and second lowest proportions in 2017 and 2018, and 2018 was also the second lowest winter expansion.
Most simulations show that the Arctic Ocean will be practically free of sea ice for the first time by 2050. The fate of the Antarctic sea ice is less certain.
Urgent action can change trends
In 2019 alone, 42 billion tons of CO₂ were emitted through human activities. As part of the Paris Agreement, states have committed to reducing emissions by 2030.
However, our report shows a shortage of around 15 billion tonnes of CO₂ between these commitments and avenues consistent with limiting warming to well below 2 ℃ (the less ambitious end of the Paris target). For the more ambitious 1.5 ℃ target, the gap increases to 32 billion tons.
Our report models a range of climate outcomes based on various socio-economic and political scenarios. It shows that if the emissions reductions are large and sustainable, we can continue to meet the Paris targets and avoid the worst damage to nature, the economy and people. But what is worrying is that we also have time to make it worse.
Pep Canadell, Chief Researcher, Climate Science Center, CSIRO Oceans and Atmosphere; and Executive Director, Global Carbon Project, CSIRO and Rob Jackson, Chair of the Department of Earth System Science and Chair of the Global Carbon Project at Stanford University
This article is republished by The conversation under a Creative Commons license. read this original article.