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NASA's 3D model of methane, the second-largest greenhouse gas contributor, reveals its diverse origins and its path through the atmosphere. Courtesy of NASA/Scientific Visualization StudioAs the United Nations' climate conference in Scotland highlights the urgency of addressing climate change, it's essential to grasp the scientific evidence behind global warming.
As an atmospheric scientist with a long history in global climate research and assessments, I've compiled six key insights you need to understand through charts.
What is Causing Climate Change
The main point of discussion in the negotiations is carbon dioxide, a greenhouse gas produced by burning fossil fuels — coal, oil, and natural gas — as well as from forest fires, land-use changes, and natural sources.
The late 1800s Industrial Revolution sparked a massive rise in fossil fuel consumption. It powered homes, industries, and facilitated global travel. Around the same time, scientists recognized carbon dioxide's potential to warm the planet, a concept once seen as potentially beneficial. Since the mid-1900s, systematic measurements have consistently shown a rise in carbon dioxide, with most of it directly linked to fossil fuel combustion.
Carbon dioxide remains in the atmosphere for an extended period. Some of it is absorbed by plants and oceans, but approximately half of all carbon dioxide emitted by human activities today stays in the atmosphere — and it is likely to persist for centuries, impacting global climate patterns.
In 2020, during the pandemic's first year, with fewer people driving and some industries halting temporarily, carbon dioxide emissions from fuels dropped by about 6 percent. However, this did not prevent the rise in carbon dioxide concentration because human activities released far more than nature could absorb.
If civilization were to halt all activities emitting carbon dioxide today, it would still take centuries for the concentration of carbon dioxide in the atmosphere to naturally decrease enough to restore balance to the planet's carbon cycle, due to carbon dioxide's long atmospheric lifespan.
How We Know Greenhouse Gases Can Alter the Climate
Various scientific findings point to the rise in greenhouse gas emissions over the past 150 years as a major driver of global long-term climate change. For instance:
- Laboratory tests from the 1800s onward have consistently confirmed and measured carbon dioxide's ability to absorb heat, trapping it in the atmosphere.
- Basic models based on carbon dioxide's warming effect on the atmosphere align with observed historical temperature changes.
- Advanced climate models, recently recognized with the Nobel Prize for Physics, not only suggest a warming Earth due to rising carbon dioxide, but also pinpoint the regions experiencing the most intense warming.
Historical evidence shows that when carbon dioxide levels were high, temperatures also soared. (Source: Salawitch et al., 2017, updated with data until the end of 2020.)
Springer/(CC BY-SA 4.0)Long-term data from ice cores, tree rings, and corals reveal that periods of high carbon dioxide levels correlate with higher temperatures.
Our neighboring planets provide further proof. Venus, with its carbon dioxide-heavy atmosphere, is the hottest planet in our solar system, despite Mercury being closer to the sun.
Global Temperatures Are Rising Everywhere
The increase in temperatures is evident across records from all continents and the oceans.
Temperatures aren't rising uniformly across the globe. Various factors, such as land use affecting solar energy absorption or reflection, local heating effects like urban heat islands, and pollution, all influence regional temperatures.
For instance, the Arctic is warming at a rate approximately three times the global average, partly due to the melting of snow and ice, which makes the surface more likely to absorb the sun's radiation instead of reflecting it. This, in turn, accelerates the retreat of snow and sea ice.
The Impact of Climate Change on Our Planet
Earth's climate system is a complex web, and even minor temperature shifts can lead to significant changes — such as those affecting snow cover and sea levels.
Changes are already occurring. Research indicates that rising temperatures are already influencing precipitation, glaciers, weather patterns, tropical cyclone activity, and extreme storms. Studies also show that the increased frequency, intensity, and duration of heat waves, for example, affect ecosystems, human lives, commerce, and agriculture.
Historical ocean water level records reveal a steady rise over the last 150 years, driven by melting glaciers and expanding ocean water due to higher temperatures, although some local variations occur because of land sinking or rising.
Although extreme events usually result from a combination of factors, climate change often intensifies their effects. Just as rising ocean levels can worsen coastal flooding, higher baseline temperatures make heatwaves more severe.
Climate scientists are working diligently to forecast future changes driven by increased carbon dioxide and other anticipated factors, such as global population growth. It's evident that temperatures will rise and precipitation patterns will shift. The precise extent of these changes depends on a range of interrelated factors.
Global temperatures are climbing, as shown in the chart on the left.
The ConversationSome Reasons to be Optimistic
On a positive note, scientific advancements are enhancing our comprehension of the climate and the intricate Earth system, helping us pinpoint the most at-risk areas and directing efforts to minimize the causes of climate change. Research into renewable energy, alternative energy solutions, and methods to capture carbon from industries or the atmosphere is offering more avenues for a society that’s better prepared for the future.
At the same time, individuals are becoming more aware of how they can lessen their environmental footprint, recognizing the necessity of a coordinated global response to make a substantial difference. Electric vehicles, as well as solar and wind energy, are expanding at unprecedented speeds. A growing number of people are embracing a readiness to adopt innovative strategies that promote energy efficiency, sustainable consumption, and the use of renewable energy.
Scientists are increasingly acknowledging that transitioning away from fossil fuels offers extra advantages, such as better air quality that benefits human health and the environment.
This article is republished from The Conversation under a Creative Commons license. You can access the original article here.
Betsy Weatherhead is a senior scientist at the University of Colorado, Boulder. She received the Nobel Peace Prize in 2007 for her role as a member of the Intergovernmental Panel on Climate Change, contributing to a better understanding of the Arctic climate.
