Climate change is altering the climate all over the world. What exactly is it?
The science of climate change is more solid and widely agreed upon than you might think. But the scope of the topic, as well as rampant disinformation, can make it hard to separate fact from fiction. Here, the New York Times science journalist, Dr. Julia Rosen, does her best to present the most accurate scientific information, and an explanation of how we know it: The Science of Climate Change Explained: Facts, Evidence and Proof
In early August 2021, the IPCC released the Working Group I report which provide an assessment of the current evidence on the physical science of climate change, knowledge evaluation gained from observations, reanalyses, paleoclimate archives and climate model simulations, as well as physical, chemical and biological climate processes.
Scientists are observing changes in the Earth’s climate in every region and across the whole climate system, according to the latest Intergovernmental Panel on Climate Change (IPCC) Report, released today. Many of the changes observed in the climate are unprecedented in thousands, if not hundreds of thousands of years, and some of the changes already set in motion—such as continued sea level rise—are irreversible over hundreds to thousands of years. However, strong and sustained reductions in emissions of carbon dioxide (CO2) and other greenhouse gases would limit climate change. While benefits for air quality would come quickly, it could take 20-30 years to see global temperatures stabilize, according to the IPCC Working Group I report, Climate Change 2021: the Physical Science Basis, approved on Friday by 195 member governments of the IPCC, through a virtual approval session that was held over two weeks starting on July 26.
The Working Group I report is the first instalment of the IPCC’s Sixth Assessment Report (AR6), which will be completed in 2022. “This report reflects extraordinary efforts under exceptional circumstances,” said Hoesung Lee, Chair of the IPCC. “The innovations in this report, and advances in climate science that it reflects, provide an invaluable input into climate negotiations and decision-making.” Faster warming
The report provides new estimates of the chances of crossing the global warming level of 1.5°C in the next decades, and finds that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting warming to close to 1.5°C or even 2°C will be beyond reach.
The report shows that emissions of greenhouse gases from human activities are responsible for approximately 1.1°C of warming since 1850-1900, and finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5°C of warming. This assessment is based on improved observational datasets to assess historical warming, as well progress in scientific understanding of the response of the climate system to human-caused greenhouse gas emissions.
“This report is a reality check,” said IPCC Working Group I Co-Chair Valérie Masson-Delmotte. “We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare.”
Every region facing increasing changes
Many characteristics of climate change directly depend on the level of global warming, but what people experience is often very different to the global average. For example, warming over land is larger than the global average, and it is more than twice as high in the Arctic.
“Climate change is already affecting every region on Earth, in multiple ways. The changes we experience will increase with additional warming,” said IPCC Working Group I Co-Chair Panmao Zhai.
The report projects that in the coming decades climate changes will increase in all regions. For 1.5°C of global warming, there will be increasing heat waves, longer warm seasons and shorter cold seasons. At 2°C of global warming, heat extremes would more often reach critical tolerance thresholds for agriculture and health, the report shows.
But it is not just about temperature. Climate change is bringing multiple different changes in different regions – which will all increase with further warming. These include changes to wetness and dryness, to winds, snow and ice, coastal areas and oceans. For example:
Climate change is intensifying the water cycle. This brings more intense rainfall and associated flooding, as well as more intense drought in many regions.
Climate change is affecting rainfall patterns. In high latitudes, precipitation is likely to increase, while it is projected to decrease over large parts of the subtropics. Changes to monsoon precipitation are expected, which will vary by region.
Coastal areas will see continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding in low-lying areas and coastal erosion. Extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century.
Further warming will amplify permafrost thawing, and the loss of seasonal snow cover, melting of glaciers and ice sheets, and loss of summer Arctic sea ice.
Changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels have been clearly linked to human influence. These changes affect both ocean ecosystems and the people that rely on them, and they will continue throughout at least the rest of this century.
For cities, some aspects of climate change may be amplified, including heat (since urban areas are usually warmer than their surroundings), flooding from heavy precipitation events and sea level rise in coastal cities.
For the first time, the Sixth Assessment Report provides a more detailed regional assessment of climate change, including a focus on useful information that can inform risk assessment, adaptation, and other decision-making, and a new framework that helps translate physical changes in the climate – heat, cold, rain, drought, snow, wind, coastal flooding and more – into what they mean for society and ecosystems.
This regional information can be explored in detail in the newly developed Interactive Atlas interactive-atlas.ipcc.ch as well as regional fact sheets, the technical summary, and underlying report.
Human influence on the past and future climate
“It has been clear for decades that the Earth’s climate is changing, and the role of human influence on the climate system is undisputed,” said Masson-Delmotte. Yet the new report also reflects major advances in the science of attribution – understanding the role of climate change in intensifying specific weather and climate events such as extreme heat waves and heavy rainfall events. The report also shows that human actions still have the potential to determine the future course of climate. The evidence is clear that carbon dioxide (CO2) is the main driver of climate change, even as other greenhouse gases and air pollutants also affect the climate. “Stabilizing the climate will require strong, rapid, and sustained reductions in greenhouse gas emissions, and reaching net zero CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have benefits both for health and the climate,” said Zhai.
“Stabilizing the climate will require strong, rapid, and sustained reductions in greenhouse gas emissions, and reaching net zero CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have benefits both for health and the climate. IPCC Working Group I Co-Chair Panmao Zhai.
United Nations Framework ~ 2015
This project was especially timely as it coincided with the 2015 United Nations Framework Convention on Climate Change, otherwise known as the 2015 Paris Climate Summit. The purpose of this event is achieving a new international agreement on the climate, applicable to all countries, with the aim of keeping global warming below 2°C. As a result of this convention, a landmark agreement was reached on December 12, 2015, charting a new course in the 2-decade old global climate effort. 195 countries reached a history making agreement to reduce their greenhouse gas emissions in order to avert the most dire effects of climate change. This groundbreaking pact requires every country, large and small, to take action. To learn more, see "Understanding the Paris Climate Accord and Its Implications".
The Union of Concerned Scientists is a national nonprofit organization founded more than 50 years ago with the mission to use rigorous, independent science to solve our planet's most pressing problems. They combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future. Their recommendations include:
Cutting emissions-To achieve net zero emissions, we need a massive transformation in how we produce and consume electricity. We need a newer, better transportation system. We need to stop deforestation. We need a climate-friendly agricultural system.
Removing carbon dioxide- The easiest way to do this is by planting new forests (afforestation) or restoring old ones (reforestation). Other enhanced land management practices can help, as can new technologies that suck CO2 out of the air (“direct air capture”), or prevent it from leaving smokestacks (“carbon capture and storage”).
Fighting disinformation-For years, media pundits, partisan think tanks, and special interest groups funded by fossil fuel companies have raised doubts about the truth of global warming...This barrage of disinformation misleads and confuses the public about the growing consequences of global warming and makes it more difficult to implement the solutions we really need.
Prepare and adapt- Cutting carbon is the only long-term solution for avoiding climate impacts. In the short-term, we need to adapt. That means everything from discouraging development in high-risk areas, to planning for water scarcity, to building more resilient cities and communities. Investments should be scientifically sound and socially just, and focused where the impacts are greatest—often in low-income communities and communities of color.
"Science suggests that we can avoid the worst impacts of climate change if we limit warming to under 2ºC. To do so, we need a much cleaner economy by mid-century or sooner. Fossil fuel companies need to stop preventing climate action."
Looking for more resources for different grade levels? The CLEAN Collection is a hand-picked and rigorously reviewed collection of educational resources aligned with the Climate Literacy and Energy Literacy frameworks. The review process engages scientists and educators in vetting each resource for scientific accuracy, pedagogic effectiveness and useability.
The Climate Reality Project, founded by Nobel Laureate and former U.S. Vice-President Al Gore in 2006. "The Climate Reality Project is a diverse group of passionate individuals who have come together to help solve the greatest challenge of our time, and are committed to building a better future together".