Understand Climate Change Basics
Environmental Defense Fund
Human-caused climate change has led to severe consequences and losses and damages to nature and people in every region across the globe, disproportionately impacting vulnerable communities. A better future is still possible, but it requires prompt and profound actions in all sectors this decade to drastically cut greenhouse gas emissions.
A vast body of evidence, compiled by tens of thousands of scientists from over a hundred nations, leaves no doubt: Humans are the primary drivers of climate change. Through activities like burning fossil fuels (coal, oil, and gas), raising livestock, and deforestation, we significantly increase the concentration of greenhouse gases (GHG) in the atmosphere. The thickening blanket of these heat-trapping gases has resulted in a global surface temperature rise ten times faster than any warming period in human history. Sea and land ice are melting, sea level is rising, coral reefs are dying, and extreme events are more intense and frequent from shifting moisture conditions and air circulation patterns.
Vulnerable communities, who have historically contributed the least to climate change, have been hit the hardest and often have the least resources to prepare and recover. Some of the impacts are already surpassing adaptation limits, leading to losses and damages. Scientists are certain that if we continue this path, it will be catastrophic. Every increment of warming will cause regional shifts in average climate conditions and extreme events will become more extensive and severe.
A better future is possible but only with rapid transformation this decade. According to the lntergovernmental Panel on Climate Change (IPCC), the world’s most authoritative scientific body on climate change, urgent and substantial reductions in GHG emissions are necessary to limit warming to 1.5°C, the threshold to avoid putting millions more people at risk of life-threatening consequences. This requires prompt and profound actions in all sectors to:
- Peak GHG emissions immediately and before 2025
- Halve Carbon Dioxide (CO2) emissions in the 2030s, relative to 2019
- Reach net zero CO2 emissions in the 2050s and net zero GHG emissions around the 2070s
Three Insights to a Better Future
- Reduce Major Short-Lived Climate Pollutants: This involves cutting methane emissions from agriculture, oil and gas operations, and landfills. Reducing emissions of black carbon (soot) from diesel engines and cookstoves and phasing out HFCs, commonly used as coolant in refrigerators and air conditioning, are also important.
- Achieve Net Zero Long-Lived Climate Pollutants: We must strive to emit no more long-lived climate pollutants than can be removed from the atmosphere by human-induced activities. This includes reducing emissions of long-lived climate pollutants such as carbon dioxide (CO2) and nitrous oxide (N2O) as much as possible. Investing in and scaling up removal strategies will become important in balancing out any remaining emissions that cannot be reduced. It is also crucial to protect natural ecosystems such as forests, wetlands, and oceans, which absorb and store significant amounts of CO2.
- Take Early Action to Reduce All Climate Pollutants: Prompt action yields better climate outcomes over all timescales, makes the task easier and cheaper in the long-run, and reduces reliance on nascent technologies that are not yet available at scale.
The Climate Impact of Carbon Dioxide
The Earth absorbs energy from the sun and releases it back to space as heat. About 90% of the heat is trapped by greenhouse gases and re-radiated to make the Earth a cozy and comfortable place to live. Carbon dioxide (CO2) is an important greenhouse gas naturally present in the atmosphere as a component of the planet’s carbon cycle, which involves the organic exchange of carbon among the atmosphere, oceans, soil, plants, and animals. Human activities are altering the carbon cycle by massively increasing CO2 concentrations and impacting the ability of natural carbon sinks like forests and soils to absorb and store CO2. As a long-lived gas, CO2 can accumulate in the atmosphere over time. Every bit of CO2 released into the atmosphere adds to the greenhouse effect, causing global warming.
Since the onset of the Industrial Revolution, human activities have increased the amount of CO2 in the atmosphere by 50%, reaching a level that is now 150% of its value in 1750. This significant rise in CO2 emissions, primarily from the burning of fossil fuels, is the main driver of climate change during the past century. Urgent action to transition away from fossil fuels is necessary to secure a livable planet, as the projected CO2 emissions from existing fossil fuel infrastructure without additional abatement would exceed the remaining carbon budget for limiting global warming to 1.5°C. Additionally, CO2 emissions from direct human impacts on forestry and other land use, such as through deforestation, land clearing for agriculture, and degradation of soils further contribute to the problem.
The Climate Impact of Methane
Methane is a short-lived greenhouse gas that has a heat-trapping impact over 80 times greater than carbon dioxide (CO2) over a 20-year time horizon. Even though CO2 has a longer-lasting effect, methane sets the pace for warming in the near term. Reducing methane emissions is the fastest and most effective way to slow global warming.
Methane comes from both natural and human-caused sources. It is generated during the breakdown of plant matter in wetlands and as organic waste decomposes in landfills. The agricultural sector represents a significant source of methane emissions, primarily from enteric methane (gas produced by the digestive system of ruminant animals such as cows, sheep, and goats), livestock manure decomposition, and rice cultivation. Methane emissions are also present throughout the oil and gas supply chain. Leaks from fossil fuel production and transportation contribute a substantial amount of methane to the atmosphere. Natural gas itself contains 70-90% methane.
The amount of methane in our atmosphere has more than doubled since pre-industrial times. For many years, methane was overlooked in the climate change conversation, but scientists and policymakers are increasingly recognizing that methane reductions are crucial. Slowing today’s unprecedented rate of warming can help avert our most acute climate risks, including crop loss, wildfires, extreme weather events, and rising sea levels. Acting now to reduce methane emissions will have immediate benefits to the climate that reductions in CO2 cannot provide on their own.