Plant growing on dry soil

Key Findings

The science of climate change has shown that the world is warming due to human activities. It also tells us that efforts to address climate change are not on track. The United Nations has been central to global assessments of climate science--the physical science, impacts, and solution, and each new report provides a greater clarity on the climate challenge and how we can move forward.

Climate change has not stopped for COVID19

  • Atmospheric CO2 concentrations showed no signs of peaking and have continued to increase to new records. Lockdown-related fall in emissions will not reduce CO2 concentrations.
  • Global fossil CO2 emissions rose 62% between 1990 and 2019. Transformational action can no longer be postponed if the Paris Agreement targets are to be met.
  • The average global temperature for 2016–2020 is expected to be the warmest on record, about 1.1 °C above 1850-1900.
  • Human-induced climate change is affecting life-sustaining systems, from the top of the mountains to the depths of the oceans, leading to accelerating sea-level rise, with cascading effects for ecosystems and human security.
  • Climate change impacts are most felt through changing hydrological conditions including changes in snow and ice dynamics. By 2050, the number of people at risk of floods will increase from its current level of 1.2 billion to 1.6 billion.
Key Messages from the United in Science 2020 Report

2019 as second hottest year on record

  • 2019 was the second highest on record. Only 2016 was hotter due to El Niño.
  • 2015-2019 are the five warmest years on record while 2010-2019 is the warmest decade on record.
  • On the current path of carbon dioxide emissions, temperature is expected to increase by 3 to 5 degrees Celsius by the end of century. 
Graphic showing the global annual mean temperature.

1.5ºC is possible but requires unprecedented and urgent action

  • The world is already seeing the consequences of 1ºC of global warming through more extreme weather, rising sea levels and diminishing Arctic sea ice. All countries are affected by global warming. But the impacts tend to fall disproportionately on the poor and vulnerable, as well as those least responsible for the problem.
  • Limiting warming to 1.5°C is not impossible but it would require unprecedented transitions in all aspects of society. Next 10 years are critical. Global net human-caused emissions of carbon dioxide (CO2) would need to fall by about 45 percent from 2010 levels by 2030, reaching ‘net zero’ around 2050. This means that any remaining emissions would need to be balanced by removing CO2 from the air.
  • There are clear benefits to limiting warming to 1.5°C compared to 2°C: 420 million fewer people being exposed to severe heat waves, survival of some tropical coral reefs, loss of fewer plants and animal species, and the protection of forests and wetland habitats.
  • The decisions we make now will define the world we live in and for future generations. Tackling climate change is critical to ensure that people around the world are healthy, prosperous, have food, clean air and water.
  • Today, 95% of plastic packaging material value—as much as US$120 billion annually—is lost after first use. Policies which encourage more circular, efficient use of materials (especially metals, petrochemicals and construction materials) could enhance global economic activity, as well as reduce waste and pollution.
Graphic about rising temperatures and rising risks

Climate-heating greenhouse gases hit new high

  • In 2018, levels of heat-trapping greenhouse gases in the atmosphere reached record high, 407.8 parts per million. This trend means that future generations will be confronted with increasingly severe impacts of climate change, including rising temperatures, more extreme weather, water stress, sea level rise and disruption to marine and land ecosystems.
  • Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.
  • Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. Limiting climate change would require substantial and sustained reductions in greenhouse gas emissions which, together with adaptation, can limit climate change risks.
  • Adaptation and mitigation are complementary strategies for reducing and managing the risks of climate change. Substantial emissions reductions over the next few decades can reduce climate risks in the 21st century and beyond, increase prospects for effective adaptation, reduce the costs and challenges of mitigation in the longer term and contribute to climate-resilient pathways for sustainable development.
Graphic showing the global annual mean temperature
Maps shows changes in average surface temperature and precipitation

Global greenhouse gas emissions need to fall by 7.6% each year over the next decade

  • Global greenhouse gas emissions need to fall by 7.6 per cent each year over the next decade if the world is to get back on track towards the goal of limiting temperature rises to close to 1.5 degrees Celsius. 
  • Technologies and policy knowledge already exist to cut emissions, but transformations must begin now. G20 nations account for 78 per cent of all emissions.
Graphic

Health benefits far outweigh the costs of meeting climate change goals

  • Exposure to air pollution causes 7 million deaths worldwide every year and costs an estimated US$ 5.11 trillion in welfare losses globally.
  • Meeting the goals of the Paris Agreement could save about a million lives a year worldwide by 2050 through reductions in air pollution alone.
  • Human influence on the climate system is clear, and recent anthropogenic emissions of greenhouse gases are the highest in history. Recent climate changes have had widespread impacts on human and natural systems.
  • Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems. Limiting climate change would require substantial and sustained reductions in greenhouse gas emissions which, together with adaptation, can limit climate change risks.
  • Adaptation and mitigation are complementary strategies for reducing and managing the risks of climate change. Substantial emissions reductions over the next few decades can reduce climate risks in the 21st century and beyond, increase prospects for effective adaptation, reduce the costs and challenges of mitigation in the longer term and contribute to climate-resilient pathways for sustainable development.
Chimney of a manufacturing complex

Land is a critical resource

  • Agriculture, food production, and deforestation are major drivers of climate change.
  • Land is under growing human pressure and climate change is adding to these pressures. Better land management can contribute to tackling climate change but is not the only solution. 
  • Keeping global warming to well below 2ºC can be achieved only by reducing greenhouse gas emissions from all sectors including land and food.
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Protecting the environment and addressing climate change is critical for protecting human health

  • The deteriorating global environmental situation is having a major impact on people’s health. Urgent actions are needed to protect the environment and our health.
  • The world is not on track to meet the SDGs by 2030. Further delays in climate action will increase the risks from climate change and will make it more difficult and more expensive to achieve the goals of the Paris Agreement.
  • Unless environmental protections are scaled up significantly, cities and regions in Asia, the Middle East and Africa could see millions of premature deaths by mid-century.
  • Pollutants in freshwater systems will see anti-microbial resistance become a major cause of death by 2050 and endocrine disruptors impact male and female fertility, as well as child neurodevelopment.
  • The world has the science, technology and finance it needs to move towards a more sustainable development pathway.
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Bold climate action could deliver US$26 trillion in economic benefits 

  • The benefits of smarter and clearer growth are significantly under-estimated, and that bold climate action could deliver $26 trillion in economic benefits through to 2030.
  • Switching to a clean economy could lead to over 65 million new low-carbon jobs, higher global GDP growth, increase in female employment and labor participation, and 700,000 fewer air pollution-related deaths. It also could raise $2.8 trillion in carbon price revenues and fossil fuel subsidy savings to reinvest in public priorities.
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Earth’s oceans and frozen spaces paying price for taking the heat of global warming

  • The ocean has also absorbed more than 90% of the excess heat in the climate system. Global warming is resulting in profound consequences for ecosystems and people. The ocean is warmer, more acidic and less productive. Melting glaciers and ice sheets are causing sea level rise, and coastal extreme events are becoming more severe. 
  • Arctic summer sea-ice extent has declined at a rate of approximately 12% per decade during 1979-2018. The four lowest values for winter sea-ice extent occurred between 2015 and 2019.
  • People in mountain regions are increasingly exposed to hazards and changes in water availability. Smaller glaciers found in Europe, eastern Africa, the tropical Andes and Indonesia are projected to lose more than 80% of their current ice mass by 2100 under high emission scenarios. 
  • The extent of Arctic sea ice is declining and it is getting thinner. If global warming is stabilized at 1.5°C above pre-industrial levels, the Arctic ocean would only be ice-free in September – the month with the least ice – once in every hundred years. For global warming of 2°C, this would occur up to one year in three.
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