How Does Global Warming Work?
The Atmosphere, Greenhouse Gases and Temperature
The Earth – which includes continents, islands, wilderness, cities, rivers, and oceans – is surrounded by a layer of gases called the atmosphere. There are many different gases in the atmosphere including oxygen, nitrogen, carbon dioxide, and hundreds more. This atmosphere is incredibly important: among other things, it contains oxygen for humans and other animals to breathe, and carbon dioxide to help plants grow. Ozone and other gases protect us from cosmic radiation, and meteorites burn up in the atmosphere instead of smashing into Earth. The atmosphere provides many other benefits and is vital for nature, humans, and everything else on our planet.
The atmosphere also helps keep the earth at a stable temperature, unlike the freezing vacuum of space. This happens because the Sun, a fiery ball of gases, sends out rays of heat through space. When those rays reach the Earth’s atmosphere, some heat goes back out to space – but certain gases trap some of it and keep the atmosphere a stable temperature (even through cloudy days or during the night). The gases that trap heat and keep the earth warm are called “greenhouse gases” (GHGs), mainly because they act like a glass greenhouse to keep things warm. There are many of these greenhouse gases in the atmosphere: the most important and prevalent ones are carbon dioxide (CO2) and methane (CH4) – and even though they make up a small percentage of the atmosphere, they are largely what keeps the earth from freezing and allow us to live on it.
However, the concentration of greenhouse gases in the atmosphere has been increasing since the beginning of the Industrial Revolution in 1870. That’s when people discovered fossil fuels – such as coal, oil, and natural gas – and started burning them in power plants and engines to create energy for electricity, vehicles and more. Burning these fossil fuels does more than just create energy: it also releases carbon dioxide and other greenhouse gases into the atmosphere (these are called “carbon emissions”). Those carbon emissions have drastically increased the atmospheric concentration of CO2 since the beginning of the Industrial Revolution. In 1870, CO2 levels were approximately 270 parts per million (ppm), but as of May 2018 they are over 410 ppm. Because there are more heat-trapping gases, the earth is getting warmer: the average global temperature has increased by about 1°C, or 1.8°F, since 1870. This amount of “global warming” may not seem like a lot, but it has massive global consequences.
The 2 graphs below show changes in global CO2 levels over the past 800,000 years (top) and since 1700 (bottom), until June 5, 2018. The earth has gone through variations in CO2 over many thousands of years, largely due to shifts in the sun’s output and the earth’s orbit. Over the past 800,000 years, CO2 has fluctuated between a low of 170 ppm and a high of about 300 ppm (up until the modern “industrial era”). However, we have increased CO2 levels above 400 ppm – well more than anything seen in hundreds of millennia. To see different time frames, check out the Scripps Institute of Oceanography’s “Keeling Curve” website.
This CO2 variation changes weather and other aspects of the world, such as ocean levels. During times of low CO2, the earth falls into “ice ages,” and when CO2 rises we enter “interglacials.” Just looking at ocean levels shows these variations can make a huge difference in the world around us. According to NASA’s page on climate change and sea level:
“Global sea level has fluctuated widely in the recent geologic past. It stood 4-6 meters above the present during the last interglacial period, 125,000 years ago, but was 120 m lower at the peak of the last ice age, around 20,000 years ago. A study of past sea level fluctuations provides a longer-term geologic context, which can help us better anticipate future trends.”
What will our Future be?
So, higher CO2 and other GHG levels can dramatically change the environment. Unfortunately, CO2 concentrations are still rising, and the temperature is rising with them. Humans continue to burn fossil fuels and spew greenhouse gases into the atmosphere – and the rate of carbon emissions has continued to grow over the years. Other things are also helping to increase greenhouse gas levels and global temperatures. For example, trees and forests suck CO2 out of the atmosphere in order to grow, but deforestation has taken away those forests and their ability to “sequester” carbon. Cows raised for beef and dairy burp up loads of methane, which is a much more potent greenhouse gas than CO2. And some “natural feedbacks” are releasing more GHGs as the earth warms: for example, climate change leads to more forest fires which release CO2 from burning forests, and then more warming causes more forest fires which release more CO2, and so on; frozen methane at the bottom of the oceans is starting to melt and release into the atmosphere, and “permafrost” tundras filled with frozen methane are also starting to thaw, which warms the atmosphere and leads to more melting; and because floating ice in the Arctic Ocean is disappearing as it warms, there is less reflective ice to send the sun’s heat back into space, while the exposed ocean absorbs warmth and melts even more ice.
A warmer atmosphere with higher concentrations of greenhouse gases has many climate-related and other consequences. Direct climate consequences include things such as hotter, longer and more severe heat waves; stronger and more frequent storms and other extreme weather; longer and deeper droughts; more frequent forest fires; stresses to natural environments and ecosystems; and sea level rise flooding coasts and islands worldwide. These climate consequences will impact humanity in many ways: for example, there will be infrastructure damage from storms, flooding and fires; more deaths and injuries from extreme weather and heat waves; migration away from flooding coasts, droughts and more; and political and economic tensions from all of these. It will take partnerships and collaboration to protect nature and people in this changing future.
Scientists are predicting that temperatures will continue to rise, potentially by several degrees Celsius before 2100. Global leaders and activists are putting effort and money into reducing emissions (through renewable energy, zero-emissions vehicles, lifestyle changes and more) and hopefully limiting warming in the process. This “climate mitigation” will absolutely help and may make the difference between climate change we can adapt to and a global catastrophe. Some activists and politicians have also called for specific temperature targets – usually 1.5°C or 2°C above the 20th-century average – but the reality is that every fraction of a degree can have major effects, so life under these targets will still be much different than today. In fact, we are already seeing many dramatic effects of climate change and more is on the way, and in the end even keeping under 2°C may be out of reach. This means that it’s incredibly important to prepare, adapt, and increase our resilience to climate impacts for all people.
There is widespread debate about exactly how much temperatures will rise and how quickly, especially considering the choices we make around burning fossil fuels, “land-use changes,” and efforts to “sequester” (or pull out) CO2 from the atmosphere. Models compiled by the International Panel on Climate Change (IPCC), like the ones for the graph above, are used most often by advocates and policy-makers alike – but IPCC models have also been criticized for being too conservative. Some recent studies have even argued that temperature changes could be double those of forward by “official” IPCC and government estimates.
The Consequences of a Warmer World
Different areas of the globe will be uniquely affected by climate change. Just to name a few: the American Southwest is likely to see deeper and longer droughts and heat waves, which will endanger health and jeopardize food and water supplies; South Florida, which has most of its land within a few feet of sea-level, will see regular flooding from sea-level rise and more infrastructure damage and injuries from stronger hurricanes; and Greenland will see its many glaciers and ice-sheet slowly melt away, changing the entire landscape and leading to rising oceans. Even local effects can have global consequences, as well: for example, droughts in major agricultural areas can affect food prices at regional, national or global scales; and because we live in a globalized world, damage to ports from storms or sea-level rise may threaten international trade (and the prices and availability of goods worldwide). This means that it is important to study climate impacts on different regions and use that information to plan for adaptation and resilience.
Impacts on People and Specific Populations
Climate change has many consequences on the environment and society at-large. You may have seen images of hungry polar bears without enough sea ice to stay on as they hunt for food, or “bleached” coral reefs damaged by warmer and more acidic oceans (as water absorbs CO2, it becomes more acidic). As we mentioned above, though, climate change will not just affect the “environment” and wildlife – it will also affect society and the people in it. Some examples include:
- We will see stronger and more frequent storms including hurricanes and the “atmospheric rivers” that hit the West Coast of the US. These storms will damage buildings and infrastructure (such as electricity grids), lead to flooding and landslides, and affect natural ecosystems such as coastal marshes. In terms of effects on society, there are likely to be more storm-related injuries and deaths, insurance and other financial losses, and economic disruptions from lost jobs and infrastructure. Some people may also move away from storm-damaged areas and not return home, essentially ending up as “climate refugees.”
- Many parts of the world will experience longer and deeper droughts due to climate change; because more precipitation will fall as rain and not snow, areas reliant on snowpack melt for fresh-water (such as California) may also have difficulty accessing water year-round. This will lead to water shortages for personal use, potential agricultural losses, greater risks of wildfire, worse air quality because of fewer “breathing” plants and more wildfire smoke, and even electricity shortages from less water behind hydro-electric dams. Food prices may go up, which can contribute to malnutrition and other health consequences (or economic stress, as people have less to spend elsewhere after buying more-expensive food); lack of clean water can create many public health problems; wildfires can cause injuries, deaths, and economic damage; and poor air quality exacerbates respiratory illness (among other problems).
- Extreme heat events (“heat waves”) will be more frequent, more intense temperature-wise, and longer lasting. According to one website, “Globally, extremely warm nights that used to come once in 20 years now occur every 10 years. And extremely hot summers, those more than 3 standard deviations above the historic average, are now observed in about 10% of the global land area, compared to 0.1-0.2% for the period 1951-1980.” Heat waves contribute to public health consequences including heat exhaustion and heatstroke, as well as respiratory issues from poor air quality that comes with hotter days. People tend to use more electricity for air-conditioning, which can stress the electric grid. Certain populations – including people with pre-existing health conditions, poor and elderly individuals, and people in urban areas – are more vulnerable to the consequences of extreme heat.
These climate consequences – and more – will not affect everybody equally. People of color, low-income individuals, those in developing countries, women, and other minorities have been shown to bear a disproportionate burden of the effects of climate change. Even more, those most affected by climate change are often the groups that contributed the least to it and have the fewest resources to adapt to its impacts. One group that is especially affected by climate change is people with disabilities – but so far, we have largely been left out of conversations around disproportionate burdens and ability to adapt. WID’s New Earth Disability project aims to ramp up this conversation and focus on ways to support the well-being and resilience of people with disabilities to the effects of climate change. Many leaders and activists have called for “climate justice” which recognizes this disproportionate burden and calls for a human rights approach to climate resilience; we also advocate for disability climate justice and a comprehensive approach to address our needs.
Thank you for reading about climate change, its effects, and the importance of disability climate justice. For more information, please look through the other sections of the NED website!
- National Resources Defense Council (NRDC): Global Warming 101
- The Royal Society: Basics of Climate Change
- NASA: Global Climate Change – Vital Signs of the Planet
- Climate Change 101 with Bill Nye (YouTube)
- Wikipedia on Climate Change
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