What Is Global Warming?

Global warming refers to the long-term increase in Earth's average surface temperature due to human activities, primarily the emission of greenhouse gases. According to NASA's climate data, the planet's average surface temperature has risen approximately 1.1°C (2°F) since the late 19th century, with most of the warming occurring in the past 50 years.

The Intergovernmental Panel on Climate Change (IPCC) confirms that human influence has warmed the climate at a rate unprecedented in at least the last 2,000 years. This warming is distinct from natural climate variability and is directly linked to the burning of fossil fuels, deforestation, and industrial processes.

The primary cause of global warming is the greenhouse effect—a natural process that becomes problematic when amplified by human activities. Here are the main contributors:

• Carbon Dioxide (CO₂): Released from burning fossil fuels (coal, oil, natural gas), deforestation, and industrial processes. CO₂ levels have increased by over 50% since pre-industrial times, reaching 421 ppm in 2024.
• Methane (CH₄): Emitted from livestock, landfills, rice paddies, and natural gas systems. Methane is 80 times more potent than CO₂ over a 20-year period.
• Nitrous Oxide (N₂O): Released from agricultural fertilizers and industrial processes.
• Fluorinated Gases: Synthetic gases used in refrigeration and manufacturing with extremely high warming potential.

Global warming is already causing widespread changes across the planet:

• Rising Sea Levels: Global sea level has risen about 8-9 inches since 1880, with the rate of rise accelerating. The NOAA projects seas could rise 1-4 feet by 2100.
• Extreme Weather Events: Heat waves, hurricanes, droughts, and flooding are becoming more frequent and intense. 2023 was the hottest year on record.
• Melting Ice: Arctic sea ice is declining at 13% per decade. Greenland and Antarctic ice sheets are losing mass at accelerating rates.
• Ocean Acidification: Oceans have absorbed about 30% of human-produced CO₂, becoming 30% more acidic and threatening marine ecosystems.
• Ecosystem Disruption: Species are shifting their ranges, coral reefs are bleaching, and biodiversity is declining globally.

While often used interchangeably, these terms have distinct meanings:

Global warming specifically refers to the rise in global average temperatures, primarily caused by increased concentrations of greenhouse gases in the atmosphere.

Climate change is a broader term encompassing all changes to climate patterns, including shifts in precipitation, wind patterns, and extreme weather events. Global warming is one aspect of climate change.

Scientists prefer 'climate change' because it better describes the full range of impacts, which include both warming and other changes to Earth's climate system.

The scientific understanding of global warming has evolved over nearly two centuries:

Early Discoveries (1800s)

• 1824: French physicist Joseph Fourier first described the greenhouse effect, recognizing that Earth's atmosphere traps heat.
• 1856: American scientist Eunice Newton Foote demonstrated that carbon dioxide traps heat, publishing the first paper linking CO₂ to climate.
• 1896: Swedish chemist Svante Arrhenius calculated that doubling atmospheric CO₂ could raise global temperatures by 5-6°C—remarkably close to modern estimates.

Modern Climate Science (1900s)

• 1938: Guy Callendar compiled temperature records showing warming and linked it to fossil fuel combustion.
• 1958: Charles David Keeling began continuous CO₂ measurements at Mauna Loa, creating the famous "Keeling Curve" showing rising CO₂ levels.
• 1975: The term "global warming" was first used in a scientific paper by geochemist Wallace Broecker.
• 1988: NASA scientist James Hansen testified before Congress that global warming had begun, bringing the issue to public attention.
• 1988: The Intergovernmental Panel on Climate Change (IPCC) was established by the UN.

Scientific Consensus Forms (1990s-2000s)

• 1990: First IPCC report confirmed rising temperatures and greenhouse gas concentrations.
• 1997: Kyoto Protocol adopted—first international treaty to set binding emissions targets.
• 2001: IPCC Third Assessment declared human influence on climate "likely" (>66% probability).
• 2007: IPCC Fourth Assessment upgraded to "very likely" (>90%), shared Nobel Peace Prize with Al Gore.
• 2013: IPCC Fifth Assessment stated human influence is "extremely likely" (>95%).
• 2015: Paris Agreement adopted, committing nations to limit warming to 1.5-2°C.

Despite overwhelming scientific consensus, organized opposition to climate science emerged:

Manufactured Doubt

Beginning in the late 1980s, fossil fuel companies funded campaigns to cast doubt on climate science. Internal documents from companies like ExxonMobil revealed they knew about climate change risks as early as 1977 while publicly promoting skepticism.

Think Tanks and Lobbying

Organizations funded by fossil fuel interests promoted alternative theories and attacked climate scientists. These tactics mirrored earlier campaigns by tobacco companies to deny health risks of smoking.

Political Polarization

Climate change became increasingly politicized, particularly in the United States. Despite scientific consensus, public acceptance of human-caused warming became divided along political lines.

Scientific Response

The scientific community responded by:

• Publishing multiple consensus studies showing 97%+ agreement among climate scientists
• Creating attribution science to link specific weather events to climate change
• Improving climate models that have accurately predicted observed warming
• Establishing the IPCC process for rigorous, peer-reviewed assessment reports

Today, every major scientific organization worldwide—including NASA, NOAA, the American Meteorological Society, and national academies of science from 80+ countries—affirms that climate change is real and primarily caused by human activities.

Addressing global warming requires action at individual, community, and governmental levels:

Individual Actions

• Reduce energy consumption and switch to renewable sources
• Use public transportation, bike, or drive electric vehicles
• Eat less meat and reduce food waste
• Support sustainable businesses and products

Systemic Solutions

• Transition to Clean Energy: Replace fossil fuels with solar, wind, and other renewable sources
• Carbon Pricing: Implement carbon taxes or cap-and-trade systems
• Reforestation: Protect existing forests and plant new trees to absorb CO₂
• International Cooperation: Honor commitments under the Paris Agreement to limit warming to 1.5°C

The scientific consensus on human-caused global warming is overwhelming. Over 97% of climate scientists agree that current warming trends are extremely likely due to human activities. This consensus is supported by:

• Multiple independent temperature datasets showing consistent warming
• Ice cores revealing CO₂ levels higher than any point in 800,000 years
• Attribution studies linking specific weather events to climate change
• Climate models accurately predicting observed warming patterns

Major scientific organizations worldwide, including NASA, NOAA, and national academies of science from every major country, affirm that climate change is real, human-caused, and requires urgent action.