When we talk about our changing planet, understanding the difference between climate change and climate variability is crucial. While both involve shifts in atmospheric conditions, they operate on vastly different timescales and stem from distinct causes. This distinction matters because it shapes how we respond to environmental challenges and plan for the future.
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What exactly is climate change?
The United Nations Framework Convention on Climate Change defines climate change as alterations in climate that are attributed directly or indirectly to human activity, which modifies the composition of the global atmosphere and occurs in addition to natural climate variability observed over comparable time periods. This definition emphasizes the role of human actions in driving long-term shifts in our climate system.
Unlike short-term weather fluctuations or natural cycles, climate change represents sustained transformations that persist across decades or longer. The IPCC uses a broader definition, referring to any change in the state of the climate that can be identified by changes in the mean or variability of its properties and that persists for an extended period, typically decades or longer, whether due to natural variability or human activity.
The human fingerprint on climate
Human activities have become the dominant driver of climate change since the 1800s. Burning fossil fuels like coal, oil and gas generates greenhouse gas emissions that trap heat in the atmosphere, causing temperatures to rise. According to the United Nations, since the Industrial Revolution, more than 2,000 billion metric tons of carbon dioxide have been added to the atmosphere through human activities.
The scale of anthropogenic emissions far exceeds natural sources. While volcanic eruptions are often cited as natural contributors to atmospheric carbon dioxide, research shows that human activities emit 60 or more times the amount of carbon dioxide released by volcanoes each year. In 2010 alone, human activities were responsible for approximately 35 billion metric tons of CO₂ emissions, while all volcanic emissions worldwide contributed less than 1 billion metric tons annually.
Natural versus anthropogenic factors
Natural factors like volcanic eruptions do affect climate, but their influence differs significantly from human-caused changes. Major volcanic eruptions inject sulfur dioxide into the stratosphere, which can cause temporary global cooling lasting one to two years. However, the carbon dioxide emissions from human activities greatly surpass those from volcanoes, and their warming effect persists much longer in the atmosphere.
Understanding climate variability
Climate variability refers to short-term fluctuations in atmospheric and oceanic conditions that occur naturally within the climate system. These variations happen over periods ranging from months to years and differ fundamentally from the long-term trends associated with climate change.
The most prominent example of climate variability is the El Niño-Southern Oscillation, a natural climate pattern that shifts irregularly every two to seven years. During El Niño events, sea surface temperatures in the eastern Pacific become warmer than average, while La Niña events bring cooler than average temperatures. These events cause short-term spikes or dips in global temperatures, typically lasting about one year.
How El Niño differs from long-term warming
ENSO is a naturally occurring large-scale climatic phenomenon involving fluctuating ocean temperatures in the central and eastern equatorial Pacific, coupled with changes in the overlying atmosphere. The pattern occurs in irregular cycles of two to seven years and presents three phases: El Niño, La Niña and a neutral phase.
While ENSO creates year-to-year variability in global temperatures, it doesn’t change the underlying warming trend. Recent analysis shows that global temperatures during La Niña years today are warmer than El Niño years just a few decades before, demonstrating that short-term natural variability is occurring on top of long-term human-caused warming.
The IPCC’s critical role in climate assessment
The Intergovernmental Panel on Climate Change serves as the world’s leading authority on climate science, synthesizing research from thousands of scientists worldwide. IPCC reports provide comprehensive assessments of climate change, its impacts, and potential response strategies.
The latest IPCC findings document unprecedented changes in Earth’s climate system. Already, with 1.1 degrees Celsius of global temperature rise, changes to the climate system that are unparalleled over centuries to millennia are occurring in every region, from rising sea levels to more extreme weather events to rapidly disappearing sea ice.
Rising seas and extreme weather
IPCC reports highlight multiple climate change risks, including accelerating sea level rise and intensifying extreme weather. Global mean sea level is rising and accelerating, increasing from 1.4 millimeters per year during 1901-1990 to 3.6 millimeters per year during 2006-2015, with the dominant cause being anthropogenic forcing since 1970.
The 2023 IPCC synthesis report warns that every 0.5 degree Celsius of global temperature rise will cause clearly discernible increases in the frequency and severity of heat extremes, heavy rainfall events and regional droughts. Coastal areas will see continued sea level rise throughout the 21st century, contributing to more frequent and severe coastal flooding and erosion.
Beyond 2050, sea level rise projections show the climate system will continue changing for centuries. Under high emission scenarios, extreme sea level events that previously occurred once in 100 years could happen every year by the end of this century at many coastal locations.
Why the distinction matters
Understanding the difference between climate change and variability is essential for developing effective responses to environmental challenges. Climate variability, like El Niño and La Niña, creates short-term fluctuations that require adaptive management strategies. Climate change, driven primarily by human activities, demands fundamental transformations in how we produce and consume energy, protect ecosystems, and plan for the future.
The overwhelming scientific evidence shows that while natural variability will continue to create year-to-year fluctuations, the long-term trajectory of our climate is being shaped by the greenhouse gases we emit into the atmosphere. Addressing climate change requires sustained global action to reduce emissions and build resilience to the changes already underway.
What do you think? How might understanding the difference between short-term climate variability and long-term climate change influence the way communities prepare for environmental challenges? What role should natural climate patterns like El Niño play in how we plan adaptation strategies?
References
- https://unfccc.int/resource/docs/convkp/conveng.pdf
- https://unfccc.int/files/press/backgrounders/application/pdf/press_factsh_science.pdf
- https://www.un.org/en/global-issues/climate-change
- https://www.usgs.gov/programs/VHP/volcanoes-can-affect-climate
- https://science.nasa.gov/climate-change/faq/what-do-volcanoes-have-to-do-with-climate-change/
- https://www.climate.gov/enso
- https://www.who.int/news-room/fact-sheets/detail/el-nino-southern-oscillation-(enso)
- https://ourworldindata.org/global-temperatures-el-nino-la-nina
- https://www.ipcc.ch/2021/08/09/ar6-wg1-20210809-pr/
- https://www.ipcc.ch/srocc/
- https://www.wri.org/insights/2023-ipcc-ar6-synthesis-report-climate-change-findings
- https://www.ipcc.ch/srocc/chapter/chapter-4-sea-level-rise-and-implications-for-low-lying-islands-coasts-and-communities/
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