Highlights

• Extreme heat is primarily caused by the greenhouse effect, a natural process that keeps the Earth's surface warm enough to support life.
• Human activities, such as burning fossil fuels (coal, oil, and gas) and deforestation, have intensified the greenhouse effect by releasing large amounts of greenhouse gases (carbon dioxide, methane, etc.) into the atmosphere.
• These greenhouse gases trap heat from the Sun, preventing it from escaping back into space and leading to an overall increase in the Earth's temperature, known as global warming.
• Global warming exacerbates heatwaves by creating a higher baseline temperature, making extreme heat events more frequent and intense.
• Changes in weather patterns, such as shifts in atmospheric pressure systems and the jet stream, can also influence the occurrence and persistence of extreme heat events.
• Urbanization and the development of heat-absorbing surfaces in cities (concrete, asphalt) contribute to the urban heat island effect, where cities become significantly warmer than surrounding rural areas during heatwaves.
• Natural climate variability, such as El Niño and La Niña events, can temporarily enhance or suppress extreme heat events

In recent years, extreme heat events have become more frequent and intense, impacting communities, ecosystems, and economies worldwide. Heatwaves , prolonged heat spells, and soaring temperatures during summer months have raised concerns about the reasons behind this phenomenon. As the global climate continues to warm, it becomes crucial to comprehend the factors contributing to extreme heat and the role of human activities in exacerbating these conditions. 

This view explores the main causes behind extreme heat and delves into the intricate relationship between climate change and its consequences.

The Greenhouse Effect and Climate Change

The primary driver of extreme heat is the greenhouse effect, a natural process that regulates Earth's temperature. Solar radiation passes through the Earth's atmosphere, warming its surface. As the Earth warms, it emits heat in the form of infrared radiation. Certain greenhouse gases , such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and water vapor (H2O), trap a portion of this heat in the atmosphere, preventing it from escaping into space. This retention of heat maintains a stable climate, making Earth habitable for various life forms.

However, human activities, particularly the burning of fossil fuels, deforestation, and industrial processes, have significantly increased greenhouse gas emissions. The excessive release of these gases has intensified the greenhouse effect, leading to an enhanced warming of the planet. This phenomenon, known as climate change, has resulted in more frequent and prolonged periods of extreme heat.

Amplifying Feedback Loops

Climate change has initiated feedback loops that further intensify extreme heat events. One of the most concerning feedback loops involves the thawing of permafrost in polar regions. As temperatures rise, vast amounts of organic matter trapped in permafrost start to decompose, releasing large quantities of methane, a potent greenhouse gas. This additional methane contributes to further warming, creating a vicious cycle.

Another feedback loop is related to decreasing ice cover in the Arctic. As ice melts, it reduces the Earth's surface reflectivity (albedo), causing it to absorb more sunlight rather than reflecting it back into space. This absorption of solar energy leads to higher temperatures, which, in turn, accelerates ice melting, perpetuating the cycle.

Urbanization and the Urban Heat Island Effect

Human activities have significantly altered the landscape through urbanization. Cities, with their concrete and asphalt structures, have distinct heat characteristics compared to surrounding rural areas. This phenomenon is known as the urban heat island effect .

In urban environments, concrete and asphalt absorb and retain heat during the day and release it at night, resulting in higher nighttime temperatures. Additionally, the concentration of buildings and infrastructure limits the flow of natural air currents, leading to stagnant hot air pockets. The combined effect of these factors contributes to elevated temperatures in cities compared to their rural counterparts.

Changes in Land Use and Deforestation

The conversion of natural landscapes, such as forests and grasslands, into agricultural or urban areas, has significant consequences for regional climates. Trees play a crucial role in regulating temperature through a process called evapotranspiration. This process involves the release of water vapor from leaves, which cools the surrounding air and helps maintain a stable climate.

Deforestation and land-use changes disrupt this process, leading to increased temperatures in the affected areas. Additionally, when forests are cleared, the carbon stored in trees is released into the atmosphere, further contributing to the greenhouse effect 

Oceanic Influences-El Niño and La Niña

The Earth's oceans play a vital role in modulating global weather patterns and influencing heat distribution. El Niño and La Niña are two natural phenomena that affect ocean temperatures and atmospheric circulation.

El Niño events occur when sea surface temperatures in the central and eastern Pacific Ocean become unusually warm. This disrupts normal weather patterns, leading to droughts, heatwaves, and increased temperatures in various regions worldwide.

Conversely, La Niña events involve cooler than average sea surface temperatures in the central and eastern Pacific. These events can result in cooler temperatures in some regions but also exacerbate extreme weather conditions, including heatwaves and wildfires, in others.

Jet Stream and Atmospheric Blocking

The jet stream, a high-speed, narrow air current in the upper atmosphere, plays a significant role in weather patterns. Its meandering path can influence the intensity and duration of extreme heat events. When the jet stream gets "stuck" in a particular position, a weather phenomenon known as atmospheric blocking occurs. This leads to prolonged periods of extreme heat or cold in certain regions.

Anthropogenic Factors and Extreme Heat

While natural factors have always influenced climate, the current era of extreme heat can largely be attributed to human activities. The burning of fossil fuels for energy production, transportation, and industrial processes is the main driver of increased greenhouse gas emissions. Additionally, deforestation, intensive agriculture, and urbanization have further altered local and global climate patterns, contributing to extreme heat events.

Extreme heat events are a complex interplay of natural processes and human-induced climate change. The greenhouse effect, amplified by anthropogenic emissions, lies at the heart of rising global temperatures. Feedback loops, urbanization, deforestation, and oceanic influences further exacerbate the intensity and frequency of extreme heat events. As we continue to witness the impacts of extreme heat on ecosystems and communities, it becomes evident that addressing climate change through sustainable practices and reducing greenhouse gas emissions is imperative for mitigating its adverse effects and safeguarding the planet's future.