Global Warming
Global warming refers to the gradual increase in the Earth's average temperature over the course of a century or longer, along with its associated impacts. Scientists are highly confident, with over 95% certainty, that the vast majority of global warming is a result of rising levels of greenhouse gases (GHGs) and other emissions directly caused by human activities.
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Since the start of the Industrial Revolution, the global annual temperature has risen by slightly over 1 degree Celsius, approximately 2 degrees Fahrenheit. From 1880 to 1980, it increased by an average of 0.07 degrees Celsius (0.13 degrees Fahrenheit) every 10 years. However, since 1981, this rate has more than doubled, with a rise of 0.18 degrees Celsius (0.32 degrees Fahrenheit) per decade in the last 40 years.
As a result, the Earth is experiencing unprecedented heat. Nine of the 10 warmest years since 1880 occurred after 2005, and the five warmest years on record were all since 2015. Claims by climate change deniers of a "pause" or "slowdown" in temperature rise have been debunked by numerous studies, including one published in the journal Environmental Research Letters in 2018. The impacts of global warming are already affecting people worldwide.
Climate scientists now stress the urgent need to limit global warming to 1.5 degrees Celsius by 2040 to avoid a future marked by devastating effects such as extreme droughts, wildfires, floods, tropical storms, and other climate-related disasters. These effects are felt by all individuals to some degree but disproportionately impact underprivileged, economically marginalized, and communities of color, for whom climate change often exacerbates poverty, displacement, hunger, and social unrest.
Causes for global warming
The Earth's atmosphere contains greenhouse gases such as water vapor, carbon dioxide, methane, nitrous oxide, and ozone. These gases have the ability to trap and release heat radiation within the atmosphere. As the levels of greenhouse gases increase or decrease, they impact the amount of heat retained or released from the sun. This leads to a warming, turbulent, and unpredictable atmosphere, as the heat-trapping effect of greenhouse gases intensifies in the upper layers. With each rise in carbon, methane, or other greenhouse gas levels, both local weather and global climate experience heightened agitation, heating, and instability.
Global warming is assessed by measuring the Earth's average global temperature increase. While this rise affects different regions in varying ways, the overall global temperature serves as an indicator. Greenhouse gases contribute to atmospheric heating and disturbance, leading to unpredictable weather and climate patterns, as well as intensified storms, droughts, wildfires, and extreme temperatures.
Global warming can become irreversible, meaning we will be unable to reduce dangerous levels of excess greenhouse gases (e.g., carbon) in the atmosphere to a safe pre-industrial level for hundreds to thousands of years. As of July 2023, the atmospheric carbon level has reached 420 ppm, and we are expected to enter the second phase of runaway global heating between 2025-2031, at carbon levels of 425-450 ppm.
Irreversible global warming involves a continuous increase in temperature, leading to rapid changes in the global climate that cannot be easily reversed on a practical human timescale. It becomes apparent when average global temperatures rise by 2.2°-4° Celsius (4°-7.2° Fahrenheit) above preindustrial levels.
Extinction level global warming occurs when temperatures exceed preindustrial levels by 5-6° Celsius (9-10.8° Fahrenheit) or lead to the extinction of all life on Earth or the loss of our atmosphere, known as runaway global warming. The result could be similar to what happened to Venus 4 billion years ago, with a carbon-rich atmosphere and surface temperatures reaching 462 °C.
The temperature thresholds described for irreversible and extinction level global warming are not fixed limits but range boundaries that illustrate the related consequences and their intensities within a specific level of global warming. These levels may be adjusted based on future research. Chapters 4 and 5 will delve into the complex interactions and the foundation for understanding how we are currently contributing to irreversible and extinction-level global warming if we continue our current trajectory.
Life of Co2 in the atmosphere
Currently, carbon dioxide stands as the most significant greenhouse gas contributing to global warming. Earlier beliefs by scientists suggested that once carbon dioxide enters the atmosphere, it would persist for approximately 100 years. However, recent research contradicts this assumption, revealing that 75% of the carbon dioxide will endure for thousands of years, and the remaining 25% will stay indefinitely. This newfound understanding unveils a grave global warming crisis that will have far-reaching consequences lasting much longer than previously anticipated.
"The lifetime of fossil fuel CO2 in the atmosphere spans a few centuries, with an additional 25 percent that essentially remains forever. The implications of releasing fossil fuel CO2 into the atmosphere extend far beyond our expectations... longer than Stonehenge, surpassing time capsules and nuclear waste, and far beyond the age of human civilization as we know it."
Effects of Global Warming
Every year, scientists uncover more evidence of the severe consequences of global warming, revealing its devastating effects on both humanity and the environment. As climate change intensifies, heat waves, droughts, and floods become more frequent and severe, leading to dire consequences for communities and an increase in casualties. If emissions are not curbed, experts predict that climate change could result in over 250,000 deaths worldwide each year and push 100 million people into poverty by 2030.
The United States is already experiencing the impacts of global warming, and without effective emission control, the following challenges lie ahead:
- Disappearing glaciers, early snowmelt, and severe droughts will exacerbate water shortages and escalate the risk of wildfires in the American West.
- Rising sea levels will lead to more coastal flooding, particularly on the Eastern Seaboard and in regions like Florida and the Gulf of Mexico.
- Forests, agriculture, and urban areas will face increased threats from pests, heat waves, heavy downpours, and floods, potentially causing damage to agricultural and fishing industries.
- Habitats such as coral reefs and alpine meadows may face disruption, pushing many plant and animal species toward extinction.
- Allergies, asthma, and infectious diseases will become more prevalent due to the expansion of pollen-producing ragweed, higher air pollution levels, and the proliferation of conditions favoring pathogens and mosquitoes.
Although climate change affects everyone, certain communities bear a heavier burden, especially Indigenous people, people of color, and economically disadvantaged individuals. Inequities inherent in housing, healthcare, and labor systems make these communities more vulnerable to the worst impacts of climate change, despite their minimal contributions to the issue.