What Are Heat Waves, Global Warming, and Climate Change? Their Importance and Differences

We Are Witnessing the Hottest Days of Our Lives

Daytime temperatures on Turkey's Mediterranean coast are exceeding 45 degrees. The three-headed monster of Greek mythology, “Kerberos”, gave its name to the summer 2023 heat wave that drove temperatures as high as 48 degrees on Italy's islands of Sicily and Sardinia. In European Union countries alone, heat waves caused 60 thousand deaths in 2022.

“Heat wave,” “global warming,” and “climate change” have become frequent topics of discussion among scientists, policymakers, and the public. Yet uncertainty often remains about what these terms mean, how they relate, and why they matter. This article clarifies the concepts, explains their differences, and explores why they concern everyone. As heat waves become more frequent and intense, global warming accelerates, and climate impacts grow more apparent, understanding these issues is vital not only for scientists and policymakers, but for all humanity.

What Is a Heat Wave?

A heat wave is a period of exceptionally high temperatures, usually lasting several days or longer.

There is no single precise definition because what counts as “hot” depends on the local climate and season. Generally, however, it means temperatures remaining far above normal for several days.

Heat waves generally result from high-pressure systems remaining stationary over a region. These systems block cooler air and clouds, allowing temperatures to rise and remain high for several days or longer.

Dehydration (fluid loss) is one of the most common health problems during heat waves. High temperatures increase water loss, potentially causing dehydration, headaches, fatigue, weakness, and even loss of consciousness.

Heat waves may also cause more serious health problems, such as heart attack and stroke. High temperatures can disrupt the body's normal temperature regulation, putting additional strain on the heart and circulatory system.

What Is Global Warming?

Global warming is an increase in Earth's average surface temperature.

Climate change and global warming are technically different concepts, but closely related and often discussed together.

Global warming generally results from greenhouse gases released into the atmosphere by human activities. These gases trap sunlight and heat, warming the planet. This natural process is called the “greenhouse effect,” but human activities—particularly burning fossil fuels and deforestation—strengthen and accelerate it.

What Is Climate Change?

Climate change includes global warming as well as changes in rainfall patterns, rising sea levels, melting glaciers, and other large-scale environmental and atmospheric changes.

It can result from natural processes, such as volcanic activity and changes in solar radiation, and human activities. The flooding in Turkey's Black Sea region, especially Ordu, on 10 July 2023 is a good example. Ordu experienced its most destructive flood in history, in summer.

Climate change can alter rainfall patterns, bringing heavier rain and more frequent, severe flooding to some regions. Such events may cause major damage and loss of life, particularly where infrastructure is unprepared.

However, directly attributing a specific weather event to climate change is often difficult: weather is complex and influenced by many factors. In general, climate change increases the risk of more frequent and severe events, including floods, droughts, heat waves, and other extremes.

Global warming is therefore part of climate change and generally considered one of its main drivers. Although the terms are often used interchangeably, each has a specific meaning.

Temperature Forecasts and Expectations for 2024

In early June 2024, temperatures in the shade reached 37 degrees in Istanbul, 38 in Izmir, 40 in Antalya, and 35 in Ankara. Prof. Dr. Orhan Şen, an Istanbul Technical University (İTÜ) meteorological engineering faculty member and CNN Türk meteorology adviser, said: “This heat will not end. It will intensify. We will experience a meteorological disaster this year.”

Prof. Dr. Şen said: “Istanbul could see 43 degrees this year. Last year, it reached 41.3 degrees, surpassing the 1938 record of 40.6. It was the hottest day in 85 years. Reaching 42-43 this year is very likely.”

Future Projections for Global Warming

According to World Meteorological Organization (WMO) data, the probability that global temperature will exceed preindustrial levels by 1.5 degrees at least once between 2023-2027 is estimated at 66 percent. Global temperatures are expected to reach record levels over the next 5 years with the El Nino climate pattern.

Are Heat Waves a New Problem? Their Recent History

Heat waves are known to have become more frequent and intense over the past century. This trend is directly linked to climate change and global warming. Changes in temperature and rainfall patterns can lead to more frequent, intense heat waves.

According to NASA Global Climate Change data, 2020 statistically matched 2016, the warmest year for global average surface temperature since records began in 1880. “Statistically matched” means that average temperatures in 2020 and 2016 were statistically the same, making 2020 one of the hottest years recorded.

Are the Effects of Global Warming the Same Everywhere?

According to Global Climate Change data from NOAA (the United States National Oceanic and Atmospheric Administration), warming has not been uniform, but the upward global-average trend shows that more areas have warmed than cooled.

Since 1880, land and ocean temperatures have risen by 0.08 degrees Celsius per decade; since 1981, however, the rate has more than doubled: to 0.18 °C per decade.

Below is the global warming trend recorded by NASA from 1880 to 2022:

Greater warming generally occurs over land, particularly in the Arctic (North Pole region). Global surface temperature trends between 1993 and 2022 show warming across most of the planet (yellow, orange, and red), with cooling in only a few places, mainly Southern Hemisphere oceans.

All of the warmest 10 years in the 143-year record occurred since 2010, and the last nine years (2014–2022) were the nine warmest on record.

Future warming will depend on how much carbon dioxide and other greenhouse gases we emit over coming decades. Activities such as burning fossil fuels and clearing forests currently add about 11 billion metric tons of carbon to the atmosphere each year. This exceeds what natural processes can remove, so atmospheric carbon dioxide rises annually.

If annual emissions continue growing as rapidly as they have since 2000, models project global temperatures by the century's end at least 2.8 degrees Celsius above the 1901-1960 average, and possibly 5.7 degrees higher. If emissions grow more slowly and begin falling substantially by 2050, temperatures are still projected to be at least 1.3 degrees above the first half of the 20th century, and possibly 3.3 degrees higher.

These data suggest that heat waves may become more frequent and intense, creating serious health risks, particularly for vulnerable groups and people with chronic diseases. Climate mitigation and adaptation strategies are therefore vital for public health and medical care.

We Are Beginning to See What Global Warming Means

Prof. Dr. Levent Kurnaz, Director of Boğaziçi University's Center for Climate Change and Policy Studies, said: “Over the past 3 years, certain events masked atmospheric warming. These were ocean currents. La Nina made Pacific waters cooler, concealing how much the planet had warmed. But La Nina ended around April-May, removing that masking effect. We are now beginning to see what global warming means.”

Global temperature, derived by adding temperature values from countries and continents, is reaching recent highs with the climate crisis. WMO data estimate a 66 percent probability of exceeding preindustrial levels by 1.5 degrees at least once between 2023-2027. Global temperatures are expected to reach record highs over the next 5 years with the El Nino climate pattern.

What Are the Health Effects of a Heat Wave?

According to the World Health Organization, climate change will increase global temperatures and the frequency and intensity of heat waves in the 21st century. High temperatures can harm health and cause additional deaths. Prolonged daytime and nighttime heat creates cumulative physiological stress, worsening major global causes of death such as respiratory and cardiovascular disease, diabetes, and kidney disease. Heat waves acutely affect large populations, usually for short periods, often triggering public health emergencies, excess mortality, and socioeconomic impacts. They can also cause energy shortages that disrupt health facilities, transport, and water infrastructure, reducing healthcare capacity.

India is another region affected as strongly as Mediterranean countries. Its heat waves usually occur from March to June and occasionally extend into July. Northern India averages five to six events annually. Individual events can last weeks, occur consecutively, and affect large populations.

Heat waves cause serious, unexpected deaths, health problems, agricultural losses, and economic damage.

What Is Heatstroke?

Heatstroke occurs when the body's temperature-control system fails in extreme heat.

Rising temperatures are a major public health problem, with effects ranging from a headache to increased deaths during hot periods. Aging populations, high chronic-disease prevalence, and urbanization increase these risks. Greater demand for healthcare can create additional risks.

When exposed to heat, the body's temperature-control system responds to offset its effects. Whatever the weather, the body works to maintain an average temperature of 37 degrees Celsius. As air temperature rises, it works harder to cool down. Blood vessels near the skin dilate and sweating begins. Dilation lowers blood pressure, requiring the heart to work faster and harder to maintain circulation. Heartbeat and breathing accelerate. Evaporating sweat removes heat through the skin, while reduced urine output conserves fluids.

Losing fluid and minerals through sweat causes weakness, often with headaches. Nausea, muscle cramps, and increasingly dry skin indicate worsening problems. When body temperature exceeds 40 degrees Celsius, a life-threatening condition causing multiple-organ dysfunction develops: heatstroke. Consciousness becomes clouded or is lost. If blood pressure falls too low, vital organs receive insufficient blood and heart attack risk rises. Most heat-related deaths therefore occur from heart attack and stroke caused by this bodily stress.

A person with heatstroke should immediately be moved somewhere cool and their temperature lowered with ice or cold-towel compresses. Lost fluids and minerals should be replaced with IV fluids, and blood pressure, pulse, and consciousness closely monitored.

Early Warning Systems and Their Importance

Early warning systems are vital for anticipating and mitigating extreme weather such as the increasingly frequent heat waves associated with global warming and climate change. Using advanced meteorological data and temperature observations, they predict heat waves and warn the public, particularly at-risk groups, of possible health dangers. This is especially important for older people, children, pregnant women, and people with chronic diseases.

Their effectiveness depends closely on how communities respond and prepare for extreme heat. Practical strategies are therefore essential alongside warnings: drinking plenty of fluids, using shade to stay cool, and avoiding going out during the hottest hours. Cooperation among local authorities, healthcare providers, and community organizations is also valuable. This includes public education, cooling centers in vulnerable areas, and community support networks to ensure no one is left without help during heat waves.

Final Words for Those Who Doubt Global Warming and Climate Change

Despite broad scientific consensus, some people and groups continue to deny or question global warming and climate change. They often claim that climate change is natural, human activities do not significantly affect climate, or scientists disagree. These claims generally conflict with scientific evidence. Most climate scientists agree that Earth's warming is largely caused by human activities and warn of serious, potentially devastating effects. Climate-change denial often rests on political or ideological beliefs rather than scientific facts and can obstruct effective climate policy. Informed, evidence-based discussion and action are therefore vital to addressing climate change.