Differences between global warming and climate change

The terms “global warming” and “climate change” are often used interchangeably. In the scientific literature, climate change and global warming are inextricably linked, even if they are distinct phenomena. The simplest explanation for this link is that global warming is the primary cause of changes in our current climate.

Here, we define these two concepts, describe how they are measured and studied, and explain the connection between them.

What is global warming?

The Intergovernmental Panel on Climate Change (IPCC) has defined global warming as “an increase in combined air and sea temperatures averaged over the globe over a 30-year period”. For more than a hundred years, research has been carried out to measure and identify the precise causes of global warming.

Measures throughout history

The Earth’s average surface temperature has risen and fallen throughout our planet’s history. The most comprehensive global temperature records, in which scientists have a high level of confidence, dates from 1880. Prior to 1880, observations come from farmers and scientists who, as early as the 16th century, recorded daily temperatures, precipitation measurements, and first and last frosts in their diaries. These data have often proven to be accurate when compared to instrumental data.

For long-term data, paleoclimatologists (scientists who study ancient climates) rely on historical variations in pollen counts, the advance and retreat of mountain glaciers, ice cores, chemical weathering of rocks, tree rings and species locations, shoreline changes, lake sediments, and other “proxy data”.

Scientists are constantly refining the accuracy of the recorded data and the way it is interpreted and modeled. Temperature records vary by region, altitude, instruments and other factors, but the closer we get to the present, the more certain scientists are of the facts of global warming.

NASA Earth Observatory

Natural events such as asteroid impacts and major volcanic eruptions, for example, can have dramatic effects on global temperatures, leading to mass extinctions. Cyclical changes in the position of the Earth relative to the Sun, called Milankovitch cyclescan influence global temperatures and have long-term effects on climate over thousands of years, although they do not account for the shorter-term changes observed over the past 150 years.

Indeed, for the current era, a trend emerges from the data: the average temperature of the Earth has increased much faster over the past 50 years than during any past warming event.

The greenhouse effect

From the middle of the 19th century, scientists began to identify changes in carbon dioxide concentrations as one of the main causes of global temperature changes. In 1856, American physicist Eunice Foote was the first to demonstrate how carbon dioxide absorbed solar radiation. His suggestion that “an atmosphere of this gas would give our earth a high temperature” is now the common understanding among scientists about the causes of global warming, the phenomenon now known as the greenhouse effect. In other words, higher levels of carbon dioxide and other greenhouse gases in the atmosphere translate to a warmer climate. Foote’s contribution was soon eclipsed three years later by Irish physicist John Tyndall, who is generally credited with first describing the greenhouse effect.

In 1988, James Hansen could testify before the US Congress “with a high degree of confidence” that there was “a causal relationship between the greenhouse effect and the observed warming”. Hansen was talking about recent global warming, but the “high confidence” also applies to paleoclimatology. By their very existence, since the emergence of life on Earth, carbon-based life forms have altered carbon dioxide levels in the atmosphere.

Man-made causes

Schroptschop/Getty Images

Humans have caused the fastest and most severe changes in global temperatures. Since James Hansen’s testimony in 1988, the level of confidence in the anthropogenic (human-induced) causes of global warming has become functionally unanimous within the scientific community.

These anthropogenic causes are not new. As early as 1800, naturalist Alexander von Humboldt observed how deforestation increased regional atmospheric temperatures. Just like the wildfires are breaking free today tons of carbon dioxide in the atmosphere, controlled burning has been a source of added carbon for centuries.

These traditional practices, however, are dwarfed by the number of greenhouse gases emitted since the early to late 18th century with the development of the coal-fired steam engine. Coal burning increased a hundredfold in the 19th century, increased another 50% in 1950, tripled between 1950 and 2000, and then almost doubled between 2000 and 2015. Oil consumption followed an even higher growth curve rapid, increasing 300-fold between 1880 and 1988, then increasing another 50% through 2015. Natural gas use grew the fastest, increasing a thousand-fold between the late 1880s and 1991, then another 75% until 2015.

Our world in data /CC BY-SA 4.0

Fossil fuel burning, which emits greenhouse gases mainly carbon dioxide, methane and nitrous oxide, may have peaked in 2017 but still accounted for 82% of primary energy consumption world in 2021.

The parallel growth in fossil fuel consumption and rising global surface temperatures are striking. Greenhouse gas emissions have reached levels “unprecedented for at least 800,000 years” and are “extremely likely to have been the primary cause of observed warming since the mid-20th century,” according to the IPCC.

A simple way to understand how fossil fuels contribute to global warming is to think of a blanket. The burning of fossil fuels has enveloped the Earth in a blanket of pollution, which traps heat. The more fossil fuels we burn, the thicker the blanket becomes and the more heat can be trapped.

What is climate change?

Climate is weather over a long period of time. Changes in climate created by human-induced global warming are having and will continue to have long-term effects. These effects, once thought to begin to occur in the near future, are increasingly visible today, the most apparent being changes in weather patterns. But more subtle changes to entire ecosystems also pose a very serious threat.

Extreme weather conditions

Miami is among the ten cities in the world most vulnerable to sea level rise.

tovfla / Getty Images

Global warming has made the weather wilder and more unstable, as natural disasters have shown “exponential increases over the past few decades” in both intensity and frequency. “Once in a century” natural disasters such as wildfires, deadly heat waves, droughts, floods, tropical storms, hurricanes, blizzards and avalanches have increased tenfold since 1960.

According to the World Meteorological Organization, over the past 50 years, half of all recorded disasters and 74% of associated economic losses have been due to weather, climate and water-related hazards such as floods.

Attribute time to climate change

It is often difficult to attribute a particular extreme weather event to global warming. Natural climate variability is responsible for short-term, year-to-year changes in weather patterns, especially at the regional level. But the longer-term pattern of weather events reveals the influence of climate change.

What can be attributed to global warming is climate change, where warmer oceans and air increase the likelihood and intensity of droughts, heat waves, storms, hurricanes, and other extreme weather events. The attribution of extreme events is more a matter of probability than certainty, since the circumstances involved often have no historical precedent.

But by comparing current extreme events to historical events of different intensities and different atmospheric conditions, scientists can provide increasingly rigorous explanations for the role global warming has played in worsening extreme weather.

Although there is often disagreement within the scientific community about the level of influence of climate change on a single extreme event, there is strong agreement that human-induced climate change plays a role. leading.

Threats to ecosystems

Warming waters and acidification can bleach coral colonies.

Ethan Daniels/Getty Images

More deadly than natural disasters, the threat of climate change weighs on the entire terrestrial biosphere, the ecosystems that sustain life. Species that attempt to adapt to climate change often fail.

Coral, for example, dies when the oceans absorb carbon dioxide from the atmosphere and become increasingly acidic. When peatlands and coastal wetlands dry out due to rising temperatures, their dead vegetation decomposes faster and releases greenhouse gases, contributing to a “cascading effect” where one calamity contributes to the next. Climate-related “tipping points” already underway are causing significant biodiversity loss and undermining entire ecosystems.

Research on climate change still contains unknowns and uncertainties. It is easier to understand the past than to predict the future of the physical and biological systems of an entire planet. Yet the main uncertainty is less about the hard science of climate change and more about the social science of how humans are responding to it.

Frequently Asked Questions

  • Can the climate get worse if global temperatures remain stable?

    Climate change can have cascading effects. For example, even if global temperatures remain stable, a mountain range previously forested and denuded of vegetation by drought and forest fires will retain less water in its soil, produce less water vapor through plant transpiration and will dry out the local climate.

  • If we reduced greenhouse gas emissions now, how soon would we see the effects on the climate?

    According to the IPCC, a significant reduction in emissions today would lead to lower concentrations of carbon dioxide in the atmosphere within five to ten years, which would lead to lower global surface temperatures within twenty to thirty years. . This is why it is urgent to intensify our efforts to reduce emissions immediately.

Teresa H. Sadler