What Is the Climate Crisis?
The climate crisis refers to the destabilization of the climate conditions that have allowed human communities and current ecosystems to survive and thrive on Earth. It is caused by a rise in global temperatures that scientists conclude is “unequivocally” driven by human activity — primarily the burning of fossil fuels and secondarily the destruction of forests and other natural carbon sinks. Since humans began using fossil fuels in earnest at the start of the industrial revolution, global temperatures have risen to 1.1 degrees Celsius above the 1850 to 1900 average. Global heating has now reached a rate of increase of more than 0.2 degrees Celsius per decade. This warming has already led to the melting of Arctic sea ice, the retreat of glaciers, and more frequent and intense extreme weather events like heat waves, foods and droughts. These events have already claimed lives, driven species to extinction and forced more than 13 million people from their homes in Africa and Asia in 2019 alone. With every further warming increase, the risks of additional harms become ever more severe.
Luckily, there is something we can do about it, but we have to act quickly. The latest report from the Intergovernmental Panel on Climate Change (IPCC) found that we must curb greenhouse gas emissions by 60 percent of 2019 levels by 2035 in order to limit global temperature rise to 1.5 degrees Celsius above pre-industrial levels and save hundreds of millions from suffering and poverty by 2050. Unfortunately, temperature projections based on current policies and pledges put the world on track for 2 to 3.2 degrees of warming. The climate crisis is therefore a crisis in two senses of the word. It is both “a time of intense difficulty, trouble, or danger” and “a time when a difficult or important decision must be made.” We can choose to drive our gas-powered SUVs down what UN Secretary-General António Guterres called the “highway to climate hell,” or we can turn off the ignition, take our feet off the gas pedal and walk together down a greener path.
What Are Greenhouse Gases?
Greenhouse gases get their name because they contribute to something called the greenhouse effect. When the sun’s rays penetrate the Earth’s atmosphere, these gases stop some of the heat from escaping back into space, acting like the walls of a greenhouse. Greenhouse gases already exist in the atmosphere without human intervention, and this is normally a very good thing: Without the greenhouse effect, Earth’s surface temperatures would be around 33 degrees Celsius cooler. However, human activity has released more of these gases into the atmosphere in the last two centuries, throwing the system out of balance, trapping more heat and causing global temperatures to rise.
What Are the Main Greenhouse Gases That Contribute to the Climate Crisis?
There are four main greenhouse gases causing additional warming.
Carbon Dioxide
Carbon dioxide is the greenhouse gas most responsible for heating the planet. It is a naturally occurring molecule that can be released through events like volcanic eruptions. However, since 1750, carbon dioxide concentrations in the atmosphere from the burning of fossil fuels have increased by 50 percent to reach levels not seen since around four million years ago, when sea levels were as much as 25 meters higher (approximately 82 feet) than today. In 2021, carbon dioxide reached a record 415.7 parts per million. Humans also emitted record levels of carbon dioxide over the past decade — 54 gigatonnes a year between 2012 and 2021.
Methane
Methane is a much more potent greenhouse gas than carbon dioxide — producing 28 times more warming than carbon dioxide over a 100 year period. At the same time, it lingers in the atmosphere for much shorter — around 12 years to carbon dioxide’s hundreds. The combination of methane’s potency and shorter lifespan makes reducing methane emissions a strategic priority for limiting global warming in the short term.
Methane is released both naturally — by plants decaying in wetlands — and by human activities including landfills, rice farming, the digestion of livestock animals like cows and the use of fossil fuels. Natural gas is 70 to 90 percent methane. These activities account for 50 to 65 percent of global methane emissions, and overall the gas has caused 30 percent of the post-industrial temperature hike. Indeed, the amount of methane in the atmosphere has more than doubled, reaching a record 1,908 parts per billion in 2021.
Nitrous Oxide
Nitrous oxide is a greenhouse gas primarily released by the production and use of agricultural fertilizers, though it is also emitted when fossil fuels or plant matter are burned. It is released naturally as part of the nitrogen cycle, but around 40 percent of current emissions comes from human activity. While it’s been called “a forgotten greenhouse gas” when compared to carbon dioxide and methane, it is still responsible for around 6 percent of greenhouse gas emissions. It’s also very powerful — a single molecule of nitrous oxide has 300 times the warming potential of a single molecule of carbon dioxide — and it persists in the atmosphere for around 114 years. In 2021, its atmospheric concentration reached a record 334.5 ppb, which is 124 percent of its pre-industrial levels.
Chlorofluorocarbons
Chlorofluorocarbons are the one greenhouse gas that does not occur naturally. They were created for industrial purposes and used as refrigerants, solvents and propellants for spray cans until it was discovered that they were burning a hole in the ozone layer. World leaders came together and agreed to phase out their use under the Montreal Protocol of 1987. It’s a good thing they did, because it turns out that CFCs are thousands of times more effective by mass at trapping heat than carbon dioxide. A study found that the agreement to restrict their use reduced global warming by as much as 25 percent. However, they are still occasionally emitted. A spike in 2013 was tied to illegal use in China that the nation later dealt with, but they are still released from CFC “banks” — pre-1987 insulation or cooling systems that continue to emit the chemicals.
What Are the Main Human Activities Causing the Climate Crisis?
Scientists often refer to “anthropogenic,” or human-caused, climate change. But there are really a few main human activities that are largely to blame.
Burning Fossil Fuels
The burning of fossil fuels is responsible for more than 75 percent of total greenhouse gas emissions and almost 90 percent of carbon dioxide emissions. This is because fossil fuels are made from dead and decaying lifeforms fossilized over millions of years — and carbon is the building block of life. The carbon that once helped form the DNA and proteins of ancient plants and animals is concentrated by time and pressure into coal, oil and natural gas. When these fuels are burned, that carbon once stored beneath the Earth enters the atmosphere as carbon dioxide. Leaks from fossil fuel extraction, production and transportation are also an important source of methane emissions. Many human activities currently rely on fossil fuels, from industry to heating and electricity generation to transportation. We need to find an alternative way to power these activities in order to stop overheating the atmosphere.
Land-Use Change
The second most important contribution to the climate crisis is deforestation, agriculture and other land use change, accounting for around a quarter of total greenhouse gas emissions and around 13 to 21 percent from 2010 to 2019. Trees and other plants store carbon in their trunks, leaves and roots and in the soil beneath them. When those trees are cut down or that soil is disturbed, the carbon ends up in the atmosphere and contributes to the climate crisis. What’s more, those trees and plants are no longer there to suck more carbon dioxide out of the atmosphere.
Agriculture
Tree clearing for agriculture drives more than 90 percent of tropical deforestation worldwide. In addition to getting rid of carbon sinks, the global food system emits greenhouse gases through the production and use of fertilizers and the methane-laden burps and manure of cows and other ruminants. The livestock sector as a whole is responsible for between 11.1 percent and 19.6 percent of global greenhouse gas emissions.
What Are the Main Impacts of the Climate Crisis Now and in the Future?
The climate crisis has already impacted every region on Earth. The latest IPCC report finds that both these current impacts and the risks of each increment of future warming are more severe than previously anticipated.
Hotter Temperatures
The most obvious impact of the climate crisis is an increase in temperature. Since 1970, global temperatures have increased faster than during any other 50-year period during at least the last two centuries. The last nine years are the nine warmest since record keeping began 143 years ago, and all of the 10 warmest years on record have occurred since 2010. Some scientists think 2024 might be the hottest year yet. How much temperatures continue to rise will depend on how quickly we can wean ourselves off fossil fuels. Policies in place as of 2020 put the world on track for 3.2 degrees Celsius of warming by 2100, but that could be lowered to 2 degrees Celsius if we cut greenhouse gas emissions by 35 percent by 2035 and 1.5 degrees Celsius if we cut emissions by 60 percent by the same date.
More Extreme Weather Events
The climate crisis has already led to more frequent and extreme weather events. The IPCC says it is “virtually certain” that heat waves have become more common and intense in most regions since the 1950s, with climate change the “main driver.” These heat waves have already claimed tens of thousands of lives. Most marine heat waves since at least 2006 were also likely caused by climate change, and these have doubled since the 1980s.
Because warmer air holds more moisture, the climate crisis can also lead to more extreme precipitation events, which have increased in intensity and frequency over most land areas since the 1950s. Hurricanes and other tropical storms have become wetter and more intense. Climate change has led to more or longer droughts in some regions, making the megadrought in the U.S. West 42 percent more severe. Higher temperatures and drier conditions have led to more frequent, larger and longer-lasting wildfires. If the climate continues to warm, combined heat waves and droughts and ideal wildfire conditions are expected to become more frequent. Tropical storms will continue to become more intense.
Ice Melt and Sea Level Rise
Warmer temperatures are melting ice in the world’s mountains and polar regions. The Arctic is warming nearly four times as fast as the global average, and the Greenland Ice Sheet has lost 255 gigatons of ice each year between 2008 and 2016, while Arctic sea ice has declined since 1978, with the rate of decline increasing in the last two decades and 95 percent of the oldest and thickest ice already gone. In Antarctica, ice sheets are melting at a rate of around 150 billion tons per year.
The polar ice sheets hold around two thirds of the globe’s fresh water. When they melt, that water enters the ocean, raising sea levels. To date, their melting has caused around a third of sea level rise since 1993. However, the melting of glaciers and ice sheets had driven the majority of accelerated sea level rise between 2006 and 2015. As of 2018, global sea levels had risen by 0.2 meters (approximately eight inches). In addition to polar melting, the sea level is rising because water expands as it warms. If the Greenland ice sheet were to melt entirely, it would raise sea levels by 23 feet, while the melting of all glaciers and ice sheets would raise them by more than 195 feet. While this would occur over a period of centuries, even relatively small amounts of sea level rise can threaten coastal communities with erosion, flooding, saltwater intrusion into aquifers, habitat loss and more powerful storm surges. Sea levels along the coastal U.S. are expected to rise by a foot by 2050 and two feet by 2100.
Mountain glaciers are melting as well — between 85.3 percent of Northern Hemisphere glaciers, including Greenland’s, retreated between 2000 and 2020, and nearly half of non-polar glaciers could melt by 2100 even if temperature rise is limited to 1.5 degrees. This would have devastating impacts on communities that rely on glaciers for water, power and cultural identity.
Ocean Impacts
The ocean has absorbed 90 percent of the excess heat added to the planet in the last decades, with the past 10 years being the ocean’s warmest since the 19th century. Most of this heating is occurring between zero and 700 meters (approximately 2,297 feet) from the surface. In addition to contributing to sea level rise, more intense tropical storms and the melting of sea ice, the additional heat threatens marine biodiversity through deadly marine heat waves. One of the most infamous impacts of these heat waves is coral bleaching, when warmer than average temperatures compel corals to expel the algae that give them both color and food. If temperatures rise to 2 degrees, 99 percent of tropical reefs could be lost. In general, ocean warming last century has combined with the impacts of overfishing to reduce the amount of certain fish species available for fishers.
Heat isn’t the only product of fossil fuel emissions that the ocean absorbs. It takes in around 30 percent of the carbon dioxide added to the atmosphere, leading to something called ocean acidification. Carbon dioxide dissolves in seawater into carbonic acid, which further breaks down into hydrogen ions and bicarbonate ions. Through this process, the ocean has gotten about 30 percent more acidic since the industrial revolution. When there is more hydrogen floating around in the ocean, it easily bonds with the carbonate that shell-making animals like corals and oysters need to form their shells. The decrease in carbonate is already impacting these animals, and further acidification could actually dissolve their shells. A more acidic ocean could also harm other animals like clownfish, who struggle to find their ideal habitat during their larval stage when acidity increases.
Biodiversity Loss
The ocean isn’t the only habitat where the climate crisis threatens the abundance and variety of lifeforms. The Earth is currently in the midst of a sixth mass extinction driven by human activity — losing species at a rate 1,000 times greater than any other moment in written history – and the climate crisis is an important contributor to this loss. As many as a million plant and animal species face extinction, several of them within decades.
The climate crisis is making life harder for at least 10,967 species on the IUCN Red List of Threatened Species, hastening extinction through extreme weather events, wildfires, and the spread of pests and diseases. As conditions change within a species’ range, some will be able to move into better conditions but not all will be able to relocate quickly enough. A 2020 study found that plants and animals living in areas that saw a significant increase in maximum possible temperature were more likely to be wiped out locally. By 2070, 30 to 55 percent of those species could become entirely extinct depending on how successful we are at controlling emissions.
Food and Freshwater Scarcity
All of these changes to natural processes and ecosystems will not leave human society unaffected. Already, the climate crisis is increasing both food and water insecurity through drought, ocean warming and acidification and the loss of sea ice that Indigenous Arctic communities rely on for hunting. Partly because of climate change, around half of the world’s population endures “severe water scarcity” for at least some of the year.
All of this will only get worse. Around 22 percent of the world’s population relies on glaciers for their primary source of drinking water, and future melting could deprive them of this essential resource. Saltwater intrusion from sea level rise also threatens to inundate the freshwater supply of people living on low-lying atolls. As crop yields decrease as temperatures rise, this could push 43 million people below the poverty line by 2030 just in Africa.
Poverty, Conflict and Displacement
A decrease in water and food resources will inevitably push populations into poverty, exacerbate conflicts between them and force people from their homes in search of a better life. As the climate warms, its impacts will interact more often with other factors like resource competition or political tension to exacerbate conflict. For example, while the civil war in Syria cannot be blamed on climate change alone, there is evidence that it was inflamed by the worst multi-year drought the country had seen in 900 years.
The war sparked a refugee crisis, with 5.5 million Syrians now living in other countries after fleeing the violence. Between 2010 and 2019, extreme weather events directly displaced around 23.1 million people each year. A recent Somalia-based study found that a 50 millimeter reduction in monthly rainfall could increase displacement by a factor of two, and a monthly temperature rise of 1 degree Celsius could increase displacement by a factor of 10. Depending on how much is done to curb emissions, one billion people could be climate refugees by 2050.
Human Health
The Lancet’s 2022 report on climate change and health concluded that human health was already “at the mercy of fossil fuels.” The number of heat-related deaths for people older than 65 increased by around 68 percent from 2000 to 2004 and from 2017 to 2021. Extreme weather events expose people to health hazards like increased wildfire smoke and infectious diseases that spread when drought puts sanitation at risk. Heat waves and other extreme weather events can have a negative impact on mental health, not to mention the growing issue of climate anxiety.
The range of disease-carrying organisms is already expanding as temperatures warm. For example, between 2012 and 2021, the ideal climate for the transmission of dengue by the Aedes aegypti and Aedes albopictus mosquitoes increased by 11.5 percent and 12 percent respectively. In the future, even more climate change could interact with other factors like urbanization to increase the risk of future pandemics.
Who Is Most Responsible?
All of humanity is not equally responsible for the climate crisis. Certain nations, companies and individuals have emitted significantly more greenhouse gases than others.
Countries
Historically, the U.S. is the country that has emitted the most climate-warming emissions, contributing around 20 percent to the total between 1850 and 2021. It is followed by China at 11 percent, Russia at 7 percent, Brazil at 5 percent and Indonesia at 4 percent. The culpability of the latter two is largely because of deforestation. Former colonial and industrial powers Germany and the UK contributed 4 and 3 percent respectively, but this doesn’t include emissions from their overseas colonies. A different set of calculations found that the UK and EU were together responsible for 22 percent of emissions between 1751 and 2017, while the U.S. was responsible for a quarter.
Today, China emits the most of any nation followed by the U.S., India, the EU, Russia, Japan, Brazil, Indonesia, Iran and Canada. Together, these countries are responsible for more than two-thirds of global emissions, and the top three are responsible for 42.6 percent. In comparison, the 100 least-emitting countries only contribute a modest 2.9 percent.
Companies
Certain companies — especially fossil fuel and meat and dairy companies — contribute disproportionately to the climate crisis because their business models are bound up with either burning oil, gas or coal or clearing biodiversity for agriculture. Only 100 fossil fuel companies — including ExxonMobil, Shell, BP and Chevron — have contributed 71 percent of global emissions since 1988, one study found. Not to be left out, the top five meat and dairy companies in the world have a carbon footprint equal to Exxon’s.
But the fossil fuel industry’s responsibility extends beyond its product. In recent years, evidence has emerged that most if not all of the major oil and gas companies were aware of the dangers posed by their actions in the 1970s and 80s but instead chose to fund climate denial and lobby politicians against shifting to renewable energy. Based on both their emissions and their political actions, a recent study calculated that the 21 largest fossil fuel companies owe the world at least $5.4 trillion in reparations.
Individuals
For the most part, individuals are not the driving force behind climate change. Even if you drive a gas-powered car an hour and back to work each day or heat your home with electricity from a coal-powered plant, your choices are largely shaped by the economic pressures and energy and transportation infrastructure that scaffolds your life. However, there is an exception: uber-wealthy individuals who ride in private jets and invest in polluting industries.
A 2022 study found that the wealthiest 10 percent of people on Earth were responsible for almost half of global emissions. While there is a large gap between the emissions of individuals in wealthier and poorer countries, there is now a greater gap between the emissions of wealthy and poorer individuals within the same country. The poorest 50 percent of the U.S population, for example, is actually emitting at close to the nation’s 2030 per capita emissions goal, while the richest 10 percent would need to slash their emissions by 86 percent to meet it.
Why Is the Climate Crisis a Social Justice Issue?
The disparity in responsibility for the climate crisis is why the IPCC emphasized climate justice in its most recent report. “Climate justice is crucial because those who have contributed least to climate change are being disproportionately affected,” report author Dr. Aditi Mukherji said in a statement upon its release. “Almost half of the world’s population lives in regions that are highly vulnerable to climate change. In the last decade, deaths from floods, droughts and storms were 15 times higher in highly vulnerable regions.”
What’s more, the climate crisis can exacerbate existing inequalities, making life harder for racial minorities trapped by historic redlining in urban heat islands, women in agriculture who already face pay discrimination before having to contend with climate shocks or low-income people in previously colonized countries who must now endure drought or severe storms. Responding urgently and equitably to the climate crisis is therefore essential from a social justice perspective, both to avoid the widening of existing gaps and to take the opportunity to close them as we reimagine society along more sustainable lines.
What Has Been Done About It So Far?
The international community has been talking about taking action on climate change since 1992, when the United Nations Framework Convention on Climate Change (UNFCCC) was adopted. Since then, world leaders have held 27 conferences of the parties to this convention, or COPs, at which they have made varying degrees of progress. Perhaps the most significant COP was COP 21, which met in Paris in 2015. It was here that nations negotiated the Paris Agreement to keep warming to “well below” 2 degrees Celsius above pre-industrial levels, and ideally limit it to 1.5 degrees. Nations were supposed to submit voluntary nationally determined contributions (NDC) every five years to say how much they would reduce emissions, with the end goal of reaching net zero emissions by 2050.
To date, the world is not on track to honor the Paris Agreement. For one thing, there is an “implementation gap” as current policies lag behind countries’ NDCs. Policies in place as of 2020 would put the world on track for 3.2 degrees Celsius of warming, while aligning policies with pre-COP26 NDCs through 2030 would limit it to around 2.8 degrees. Since COP26, nations have come forward with more ambitious pledges and net-zero promises. Accounting for these pledges could lower warming to 2.4 to 2.6 degrees Celsius. By considering longer term or net-zero pledges, Climate Action Tracker saw a possibility for 2 degrees of warming, and an even more optimistic 1.8 degrees when including net zero promises in effect or in discussion from around 140 countries.
While existing actions and policies are not sufficient, they have already made a difference. Policies to improve energy efficiency, halt deforestation or develop renewable energy sources have likely prevented several gigatons of carbon dioxide a year from entering the atmosphere. Progress already made has rendered the worst-case emissions scenario, which assumed a 500 percent increase in coal use and projected a 6-degree-Celsius temperature rise by 2100, “exceedingly unlikely.” That said, a 3-degree warmer world would still mean the near eradication of both coral reefs and Arctic sea ice and more days in which heat and humidity would reach dangerous levels for human survival. And the latest IPCC assessment cycle found that the temperature threshold for various risks — such as extreme weather events or threatened systems — was lower than previously estimated. Honoring the Paris Agreement goal is more urgent than ever.
What Still Needs to Be Done?
Climate action falls into two broad categories: mitigation and adaptation. Mitigation means actively reducing the amount of greenhouse gases in the atmosphere to stabilize global temperatures, while adaptation means adjusting to the changes in sea level or weather patterns that are already locked in.
Mitigation
The most important thing that can be done to stave off additional climate change is to stop burning fossil fuels as soon as possible. This means both not developing any new fossil fuel projects and even ceasing to exploit the deposits that already exist. The IPCC found that emissions from already existing fossil fuel infrastructure would gobble up the remaining carbon budget for limiting warming to 1.5 degrees Celsius, unless those emissions were somehow offset or removed from the atmosphere with still-unreliable carbon capture technology.
In order to have a 50 percent shot at the 1.5 target, greenhouse gas emissions must fall by 60 percent by 2035. This can be achieved by shifting rapidly to renewable sources of energy like wind and solar, replacing gas-fueled cars and trucks with electric vehicles and improved public transit, designing more sustainable cities, boosting the energy efficiency of buildings, decarbonizing industry, making agriculture more sustainable, protecting and restoring natural carbon sinks like forests and actively removing carbon dioxide from the atmosphere through carbon capture and storage.
Adaptation
Human activity has warmed the atmosphere enough that some climate impacts are already occurring and likely to continue. However, we can change how we design communities and infrastructure to make them more resilient to these changes. For example, the Billion Oyster Project in New York is restoring the city’s oyster reefs in part to protect it against storm surges and sea level rise, while the government of California is learning from the once-banned Indigenous practice of controlled burns to prevent larger fires. Farmers on the coast of Vietnam have begun keeping bees to help with mangrove restoration instead of gathering dwindling snails and crabs, while El Salvador is protecting itself from floods and landslides by restoring its surrounding forests.
When it comes to adaptation, there is still more work to be done. The 2022 UN Adaptation Gap report found that 84 percent of countries participating in the UN Framework Convention on Climate Change had some kind of adaptation plan, up 5 percent from the year before. However, funding for adaptation in the Global South is five to 10 times less than it needs to be, and the gap is widening instead of shrinking.
Political and Social Change
The climate crisis isn’t merely a technological problem caused by how we power our daily lives. It’s a political problem caused by an economic and political system that often prioritizes the short-term profits of large corporations over the long-term well-being of communities and ecosystems and considers nature as “resources” to be exploited for economic gain.
Therefore, solving the climate crisis means making fundamental changes to the way we write our laws and structure our society. This could include things like giving rights to nature, so that communities have a legal recourse to protect forests from destruction or waterways from pollution, or ideas like degrowth and doughnut economics that seek to reorganize the economy around meeting everyone’s essential needs without overtaxing our planetary support system. Many activists are calling for ideas like a Green New Deal or a just transition that would use mitigating and adapting to the climate crisis as an opportunity to address and resolve long-standing inequalities and make sure that when we transition to a new form of energy, no one is left behind.
Takeaway
The climate crisis may be the single greatest challenge humans have faced as a species. Every day seems to bring a new unprecedented weather event or another study warning about unsustainable emissions use or unavoidable climate impacts. But that doesn’t mean we should give up hope. While not everyone is equally to blame for climate change, everyone can play a role in the solution, from reducing one’s carbon footprint to experimenting with alternative, more sustainable forms of community to participating in climate activism to put pressure on world leaders or fossil fuel executives. The good news is that many climate solutions — from clean energy to urban trees — would make the world healthier, greener, more just and all around more pleasant to live in. Change is inevitable, but if we come together to stop burning fossil fuels and adapt in a way that prioritizes the most vulnerable among us, there’s still a chance that it can be change for the better.
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