Climate Change
Boundary Breached
The change in the ratio of incoming and outgoing energy of the Earth, caused by increased greenhouse gasses and aerosols. More trapped radiation causes an increase in global temperatures and alters climate patterns.
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Importance
The Paris Agreement set a target of limiting the global temperature increase to no more than 1.5°C above pre-industrial levels. In 2023, we reached a global mean temperature increase of 1.45°C. This is already causing extreme weather events around the world, and affecting the lives of millions of people. As more energy is captured on our planet, temperatures will continue to rise in the atmosphere, oceans, and on land.
Impacts
Increasing radiative forcing means more energy is captured on our planet, raising temperatures in the atmosphere, oceans, and on land.
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The impacts of warming include, but are not limited to, modified extreme events like torrential rainfall, floods, heatwaves, and droughts. Additionally, it leads to both melting land and sea ice, rising sea levels, and repercussions for all forms of life on land and underwater.
Control Variables
The representative indicators to estimate the state of the climate change Boundary are:
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Atmospheric CO2 Concentration
Atmospheric CO2 concentrations have been continuously rising since industrialization and are now higher than at any time in the last 15 million years. It is one of the major greenhouse gasses emitted in large quantities by human activities.
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Total Anthropogenic Radiative Forcing at the Top of the Atmosphere (TOA)
"Anthropogenic radiative forcing” encompasses all human activities that affect the Earth's energy balance, not only CO2 emissions. This includes other greenhouse gasses (e.g., methane, nitrous oxide), aerosols, and land-use changes. It is a direct measure of the change in energy balance at the top of the atmosphere, indicating how much energy is being added to or subtracted from the Earth's climate system. This change is a fundamental driver of Climate Change. Since the onset of the Anthropocene, global TOA has shown a steep and continuing rise.
Global Map of Changes in Energy Balance
The changes in energy balance over the last 20 years vary from region to region, but clearly show a general warming trend.
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Key Drivers
Fossil fuel burning directly increases CO2 concentration, which subsequently affects total radiative forcing.
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A second pathway involves non-CO2 greenhouse gas emissions, aerosols from sources such as agriculture, and changes in albedo resulting from land-use changes and natural ecosystem degradation. Aerosols and land-use changes exemplify how the Climate Change boundary is closely linked to other Planetary Boundaries. Changes in any environmental domain can impact Climate Change, highlighting the interconnected nature of the Planetary Boundary processes.
Connected Tipping Points
If the status of this Planetary Boundary continues to deteriorate, it will push many tipping elements toward tipping, including:
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The death of warm-water coral reefs
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The collapse of the Greenland and West Antarctic Ice Sheet
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Collapse of the North Atlantic Subpolar Gyre (SPG)
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Continued retreats of glaciers
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Dieback Amazon rainforest
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Collapse of the Atlantic Meridional Overturning Circulation
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Changes to the West African Monsoon (WAM)
Read more about other Boundaries
Planetary Boundary process inside Earth's safe operating space
Planetary Boundary process outside Earth's safe operating space
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