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The main scientific organizations specializing in the climate have joined forces to produce a landmark report for the United Nations Climate Action Summit that they have called “United in Science”, in which they highlight the worrying and growing gap between the agreed goals to address global warming and the real situation.
The report United in Science Includes details on the state of the climate and presents trends in atmospheric emissions and concentrations of the main greenhouse gases. It also highlights the urgency of a fundamental socio-economic transformation in key sectors such as energy and land use to avoid a dangerous rise in global temperature, with potentially irreversible impacts. It also examines tools to support climate change mitigation and adaptation.
“The report provides a unified assessment of the state of our Earth system under the increasing influence of climate change, humanity's response so far, and the far-reaching transformations that science projects for our climate in the future. The scientific data and findings presented in the report represent the latest authoritative information on these issues, ”said the UN Secretary General's Climate Science Advisory Group to the UN Secretary-General's Summit on Climate Action.
"The report highlights the urgent need to develop concrete actions to stop global warming and the worst effects of climate change," the scientists added.
The advisory group is co-chaired by the Secretary General of the World Meteorological Organization (WMO), Petteri Taalas, and the former Vice Chancellor of the TERI School of Advanced Studies Leena Srivastava, and is composed of highly recognized and respected natural and social scientists, with experience in different aspects of change. climate, including mitigation and adaptation.
The report, which was coordinated by WMO, aims to transparently display the latest in the field of authoritative and applicable science.
The report synthesis consists of brief summaries from contributing agencies: WMO, United Nations Environment Program, Global Atmosphere Watch, Global Carbon Project, Intergovernmental Panel on Climate Change (IPCC), Future Earth, Earth League and the Global Framework for Climate Services. This summary is complemented by longer individual reports, presented in a package to the high-level scientific event on September 22 and then to world leaders at the Climate Action Summit on September 23.
The world climate 2015-2019
The warmest five-year period on record
The global average temperature from 2015 to 2019 is on track to be the warmest of any equivalent period ever recorded, currently estimated at 1.1 ° C (± 0.1 ° C) above the pre-industrial era (1850–1900). Long-lasting and widespread heat waves, record fires and other devastating events such as tropical cyclones, floods and droughts have had a major impact on socio-economic development and the environment.
Continued decline in sea ice and ice mass
Arctic summer sea ice extent has decreased at a rate of approximately 12% per decade from 1979 to 2018. The four lowest measurements of winter sea ice extent occurred between 2015 and 2019.
Overall, the amount of ice lost annually in the Antarctic ice sheet increased at least six times between 1979 and 2017. The loss of glacier mass in the 2015-2019 period is the highest of any five-year period on record.
Sea level rise is accelerating, oceans are becoming more acidic
The observed rate of mean sea level rise accelerated from 3.04 millimeters per year (mm / year) during the 1997–2006 period to approximately 4 mm / year during the 2007–2016 period. This is due to a higher rate of warming and melting of the Greenland and West Antarctic ice sheets. There has been a general 26% increase in ocean acidity since the beginning of the industrial age.
Record greenhouse gas concentrations in the atmosphere
WMO Global Atmospheric Watch
The levels of the main long-lived greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), have reached new highs.
The last time the Earth's atmosphere contained 400 parts per million of CO2It was about 3-5 million years ago, when the global mean surface temperature was 2-3 ° C warmer than it is today, the ice sheets of Greenland and West Antarctica melted, parts of the ice of East Antarctica receded, everything which caused a sea level rise of 10-20 m compared to the current one.
In 2018, the global concentration of CO2 was 407.8 parts per million (ppm), 2.2 ppm more than in 2017. Preliminary data from a subset of greenhouse gas monitoring sites indicate that CO concentrations2 They are on track to reach or even exceed 410 ppm by the end of 2019.
In 2017, the global average atmospheric concentrations of CO2 was 405.6 ± 0.1 ppm, from CH4 was 1859 ± 2 parts per billion (ppb) and N2Ofue 329.9 ± 0.1 ppb. These values constitute, respectively, an increase of 146%, 257% and 122% compared to the pre-industrial levels (before 1750).
The average growth rate of CO2 over three consecutive decades (1985–1995, 1995–2005, and 2005–2015) went from 1.42 ppm / year to 1.86 ppm / year and 2.06 ppm / year, respectively.
World Carbon Budget
Global Carbon Project
Carbon dioxide emissions grew 2% and reached a record 37,000 million tons of CO2in 2018. There are still no signs that global emissions will peak before finally starting to decline, although they are growing more slowly than the world economy.
Current economic and energy trends suggest that emissions will be at least as high in 2019 as in 2018. World GDP is expected to grow 3.2% in 2019, and if the global economy decarbonizes at the same rate as in the last 10 years, Global emissions would continue to rise.
Despite the extraordinary growth of renewables in the last decade, the global energy system is still dominated by fossil fuel sources. The annual increase in global energy use is greater than the expansion of renewable energy, which means that the use of fossil fuels continues to grow. This growth must stop immediately.
The decarbonization needed to stabilize the climate requires an acceleration in the use of carbon-free energy sources and a rapid decline in the global share of fossil fuels in the energy mix. This dual requirement illustrates the scale of the challenge.
Natural CO sinks2, like vegetation and oceans, which remove about half of all emissions from human activities, will be less efficient. This underscores the need to reduce deforestation and expand natural CO sinks.2, particularly those in forests and soils, which can be improved through better management and restoration of habitats.
The emissions gap - where are we and where should we go
United Nations Environment Program
The United Nations Environment Program Emissions Gap Report, the tenth edition of which will be published this November, assesses the latest scientific studies on current and estimated future greenhouse gas emissions, and compares them to levels of greenhouse gas emissions. emissions allowed for the world to progress on a lower cost path to achieve the Paris Agreement targets. This difference between “where we are likely to be and where we should be” is known as the emissions gap.
If current climate policies and ambition levels of Nationally Determined Contributions (NDCs) are maintained, global emissions are not expected to peak in 2030, much less in 2020. Preliminary results from the Emission Gap Report 2019 indicate that greenhouse gas emissions continued to increase in 2018.
The projected emissions gap for 2030 between the emission levels under the full implementation of the conditional NDCs and the levels consistent with the least cost routes to achieve the 2 ° C target is 13 GtCO.2and. If only unconditional NDCs are implemented, the gap increases to 15 GtCO2e. For the 1.5 ° C target it is 29 GtCO2e and 32 GtCO2and respectively.
It is estimated that the current NDCs will reduce global emissions in 2030 by up to 6 GtCO2Compared to a scenario where current policies continue, this level of ambition needs to be tripled to align with the 2 ° C target and five times to align with the 1.5 ° C target.
If unconditional NDCs are implemented, and assuming that climate action continues consistently throughout the 21st century, we would be on track for an increase in global mean temperature of between 2.9 ° C and 3.4 ° C by 2100 relative to levels. pre-industrial.
If the ambitions of the NDCs are not immediately increased and backed by actions, it will be inevitable to exceed the 1.5 ° C threshold. If the emissions gap is not closed by 2030, the goal of limiting the temperature rise to 2 ° C may well be out of reach as well.
A substantial part of the technical potential can be achieved by scaling up and replicating existing and well-tested policies, such as switching to renewable energy sources and reforestation, which simultaneously contribute to key Sustainable Development Goals.
Intergovernmental Panel on Climate Change (IPCC)
Three special IPCC reports published in 2018 and 2019 assess complementary and specific aspects of climate change, ahead of the panel's Sixth Assessment Report.
The Special Report on Global Warming of 1.5 ° C states that limiting warming to 1.5 ° C is not physically impossible, but would require unprecedented transformations in all aspects of society. There are clear benefits to keeping warming at 1.5 ° C, compared to scenarios of 2 ° C or more. Every degree of warming matters.
Limiting warming to 1.5 ° C can go hand in hand with other global goals, such as achieving sustainable development and eradicating poverty.
The Special Report on Climate Change and the Earth emphasized that the earth is already under increasing human pressure and that climate change is a factor that intensifies these pressures. At the same time, keeping global warming well below 2ºC can only be achieved by reducing greenhouse gas emissions from all sectors, including those related to land and food.
“The report shows that better land management can help tackle climate change, but land is not the only solution. Reducing greenhouse gas emissions in all sectors, including energy, is essential to keep global warming as close as possible to 1.5 ° C above pre-industrial levels ”.
On September 25, 2019, the IPCC will publish the Special report on the ocean and cryosphere in a changing climate.
Future Earth and Earth League
Consolidated evidence reinforces the idea that human influence is the dominant cause of changes in the Earth system during a new geological era: the Anthropocene.
Increasing climate impacts increase the risks of crossing critical tipping points, that is, thresholds that could lead to far-reaching, in some cases abrupt and / or irreversible changes.
There is growing recognition that climate impacts are hitting harder and earlier than climate assessments indicated even just a decade ago.
As climate change intensifies, cities are particularly vulnerable to consequences such as heat stress. At the same time, cities can play a key role in reducing emissions locally and globally.
Strategies for mitigation and for scaling up risk adaptation management are needed in the future, not in isolation, given the pace of climate change and the magnitude of its impacts.
We will only achieve the Paris Agreement with immediate and inclusive action that encompasses: deep decarbonization complemented by ambitious policy measures, protection and enhancement of carbon sinks and biodiversity, and efforts to eliminate CO2.2 of the atmosphere.
Global Framework for Climate Services (GFCS)
Climate information and early warning services should support decision-making on climate action for adaptation.
Advisory Group Members
Co-chairs, Prof. Petteri Taalas, OMM, and Dr. Leena Srivastava, formerly of the School of Advanced Studies ofl Institute of Energy and Resources (TERI-SAS) and the International Institute for Applied Systems Analysis (IIASA), from November 15, 2019
Dr Navroz K Dubash, New Delhi Policy Research Center, India.
Dr. Brigitte Knopf, Mercator Institute for Global Commons Research and Climate Change.
Dr. Margaret Leinen, University of California Scripps Institution of Oceanography.
Dr. Heide Hackmann, International Council for Science.
Dr. Jian Liu, United Nations Environment Program.
Dr. Thelma Krug, Intergovernmental Panel on Climate Change.
Dr. Yacob Mulugetta, University College London.
Dr. Joeri Rogelj, Imperial College London.
Dr. Maisa Rojas Corradi, University of Chile.
Dr. Lisa Schipper, University of Oxford.
The synthesis report has been compiled by the World Meteorological Organization under the auspices of the 2019 United Nations Climate Action Summit Scientific Advisory Group, to bring together the latest updates related to climate science from a group of key partner organizations: the World Meteorological Organization ( WMO), UN Environment, the Intergovernmental Panel on Climate Change (IPCC), Global CarbonProject, Future Earth, Earth League and the Global Framework for Climate Services (GFCS). The content of each chapter of this report is attributable to the information published by the respective organizations.
For more information, please contact:
Clare Nullis, World Meteorological Organization: [email protected], +41 797091397
María Amparo Lasso, Regional Head of Communication for Latin America and the Caribbean, UN Environment: [email protected], +507 305-3182.