First article for the new (school) season, and I decided to jot down my thoughts on a topic that has been frequently mentioned in recent years: "climate change." Whatever happens, it's blamed on that. Wildfires? Climate change due to excessive heat (not arsonists who start the fires). Floods? Climate change due to heavy rainfall (not the draining of lakes for electoral reasons, or the licensing and legitimizing of filled-in rivers and streams, or insufficient irrigation works). Wind? Climate change... Earthquake? Probably the same...
What exactly is climate change, and to what extent is it anthropogenic? In this text, we will attempt to explore these issues a bit.
Let’s start with some temperature data from the climatic history of our planet. I will present them from the present going backward to somewhat see the climatic cycles that are observed. As expected, we have actual temperature measurements for the past few hundred years, while for previous periods, we estimate them using other indirect methods (e.g., clothing in descriptions or depictions, geological data, etc.).
Since it's summer, let's start with high temperatures and the viral post showing how the weather was presented a few years ago (if I found it correctly, in 2016) and how it is now:
21st Century (2000 AD - Present)
2003 Heatwave in Europe: This heatwave led to the deaths of tens of thousands of people, mainly the elderly, in countries such as France, Italy, and Spain. Temperatures reached unprecedented levels.
2010 Heatwave in Russia: One of the most extreme heatwaves in Russian history, leading to wildfires and significant loss of life.
2021 Heatwave in North America: Record temperatures were recorded in the U.S. and Canada, with Canada reaching 49.6°C in the town of Lytton.
2022 Heatwave in Europe: A new temperature record was set in Britain at 40.3°C.
20th Century
1936 Heatwave in the U.S.: During the Great Depression, the U.S. experienced one of the most extreme heatwaves, with temperatures exceeding 44°C.
1980 Heatwave in the U.S.: One of the worst heatwaves of the 20th century, causing extensive crop damage and hundreds of deaths.
Little Ice Age (1300-1850 AD)
Although this was a cold period, there were also exceptionally hot summer periods, which, while not comparable to modern heatwaves, were significant for their time. This period was colder, with temperatures about 1°C lower than today.
Middle Ages (500-1500 AD)
Medieval Warm Period (950-1250 AD): This period is characterized by a warmer climate than the modern era, with relatively high temperatures in Europe and North America (possibly only a few tenths of a degree higher than pre-industrial temperatures).
500 BC
Climate of the Classical Period: Around 500 BC, the average global temperature was likely close to pre-industrial levels, around 13.5-14°C. The climatic conditions were relatively stable and favorable for human civilization.
Prehistoric Warm Periods
Holocene Thermal Maximum (around 9000 - 5000 BC): This period, following the last Ice Age, was characterized by a warmer climate and higher temperatures compared to today.
Extreme Warm Period of the Pliocene (about 3-5 million years ago): One of the warmest periods in recent geological history, with average temperatures significantly higher than today.
Average Temperature: Estimated to be about 2-3°C higher than today.
Comparison with Today: The average global temperature today is about 14°C. During the Pliocene, temperatures may have been around 16-17°C.
Warm Period of the Eocene (about 56-34 million years ago): The warmest period of the Cenozoic era, with global temperatures 10-15°C higher than today. The causes of this warming include high concentrations of CO2 in the atmosphere, increased volcanic activity, and different geographical conditions such as continental drift.
Average Temperature: Temperatures were about 10-15°C higher than today.
Comparison with Today: The average global temperature during the Eocene may have been around 24-29°C.
Extreme Warm Periods in Pre-Cenozoic History
Warm Period of the Cretaceous (145-66 million years ago): At the beginning of the Cretaceous, the temperature was also much higher than current levels. This period is characterized by high CO2 concentrations due to intense volcanic activity and the decomposition of organic deposits.
Warm Period of the Jurassic (about 201-145 million years ago): Warm climatic conditions during the era of the dinosaurs.
Average Temperature: Temperatures were about 3-5°C higher than today.
Comparison with Today: This suggests that temperatures during the Jurassic may have been around 17-19°C.
Warm Period of the Permian-Triassic (about 252 million years ago): This period was accompanied by the largest mass extinction event in Earth's history, likely due to volcanic activity and climate change.
Average Temperature: Estimated to be about 10°C higher than today at the peak of this period.
Comparison with Today: This suggests that temperatures during the Permian-Triassic may have been around 24°C.
Summary of the planet's average temperature:
Today: Approximately 14°C.
Pre-Industrial Revolution: 13.5-14°C.
Pliocene: Approximately 16-17°C.
Eocene: Approximately 24-29°C.
Permian-Triassic: Approximately 24°C.
Jurassic: Approximately 17-19°C.
These estimates are based, as mentioned, on geological and paleontological data, such as the composition of isotopes in the shells of marine organisms, plant and animal fossils, and other geochemical indicators that help us understand past climatic conditions.
Now, let's look at what followed these warm (and much warmer than our current) periods:
After many of the warm "epochs" mentioned, "ice ages" or "cold periods" followed. Below are the details of these climatic shifts:
1.Pliocene (about 3-5 million years ago)
After the warm period of the Pliocene, there was a gradual cooling of the climate, which led to the onset of the Pleistocene epoch (about 2.58 million years ago). During the Pleistocene, there were recurring cycles of glacial and interglacial periods.
2. Eocene (about 56-34 million years ago)
Following the peak of the warm Eocene period, there was a gradual cooling during the Eocene-Oligocene transition, leading to colder climatic conditions and the formation of the first large glaciers in Antarctica during the Oligocene epoch (around 34 million years ago).
3. Jurassic (about 201-145 million years ago)
The warm period of the Jurassic was followed by cooling during the Cretaceous period, although temperatures remained generally warm compared to today. The next significant cold period occurred much later, during the Pleistocene epoch.
4. Permian-Triassic (about 252 million years ago)
The warm period of the Permian-Triassic was accompanied by mass extinctions and was followed by a period of recovery and climate stabilization. Although an ice age did not immediately follow, the next significant glacial period occurred during the Pleistocene.
Summary
The climate changes following warm periods were often complex and influenced by various factors such as volcanic eruptions, changes in atmospheric composition (which, at those times, were not influenced by a species like humans through combustion), and geological changes. However, it is generally observed that after significant warm periods, the climate often cooled, sometimes leading to ice ages.
Could Our Current Warm Period Be Followed by an Ice Age?
The idea that the current warm climate could be part of a natural climate cycle that might be followed by a colder period in the distant future is an intriguing hypothesis. However, several important factors need to be considered:
Natural Climate Cycles
Long-Term Climate Cycles: Earth has indeed experienced long-term climate cycles that include warm and cold periods. These cycles are determined by various factors, such as changes in solar radiation, volcanic activity, Earth's orbital changes (Milankovitch cycles), continental drift, and more.
Pleistocene Climate Cycles: During the Pleistocene, the cycles of glaciations and interglacials (relatively warm periods) were cyclical and primarily driven by changes in Earth's orbit and tilt.
While the possibility of future cooling exists as part of natural cycles, the current warming is heavily influenced by human activities, making the future trajectory more complex and uncertain.
Anthropogenic Factors
Increase in Greenhouse Gases: The current warm period is characterized by a rapid increase in the levels of carbon dioxide (CO2) and other greenhouse gases in the atmosphere due to human activities (burning of fossil fuels, deforestation, industrial activity).
Speed of Climate Change: The current increase in temperature is believed to be happening at a much faster rate than the natural climate cycles of the past, making it difficult for ecosystems and human societies to adapt.
It is therefore possible that there is a combination of natural and anthropogenic factors. The current warm climate is not solely the result of natural climate cycles, but also of human activity that has intensified the natural greenhouse effect. In the very distant future, it is likely that the Earth will experience colder periods again, but the scale and timing of these changes will depend on the interaction between natural and anthropogenic factors.
It would be good at this point to make some comparisons between anthropogenic pollutants and natural pollutants from volcanic eruptions, for example.
Volcanic Eruptions
Short-Term Effects: Large volcanic eruptions release significant amounts of gases and particulates into the atmosphere, such as sulfur dioxide (SO2), which can form sulfuric acid aerosols. These aerosols reflect solar radiation back into space, causing surface cooling of the Earth. For example, the eruption of Mount Pinatubo in 1991 caused a global cooling of about 0.5°C for several years.
Long-Term Effects: On geological time scales, such as during the Permian-Triassic period, prolonged volcanic activity can release large amounts of carbon dioxide (CO2) and contribute to warmer climatic conditions. However, such events can last millions of years.
Anthropogenic Emissions
Carbon Dioxide (CO2): Since the Industrial Revolution, human activities such as burning fossil fuels, deforestation, and industrial processes have released enormous amounts of CO2 into the atmosphere. The concentration of CO2 has increased from approximately 280 ppm (parts per million) before the industrial revolution to over 410 ppm today.
Rate of Emissions: The rate of CO2 emissions from human activities is much higher compared to natural rates of change. For example, the annual CO2 emissions from human activities are about 100 times greater than volcanic emissions in an average year.
Volcanic eruptions can have significant short-term and long-term impacts, but they generally lead to short-term cooling (due to aerosols) and may cause long-term warming only on geological timescales. Human-generated CO2 emissions have a direct and continuous effect on increasing the planet's temperature as long as they continue. The massive burning of fossil fuels in recent decades has significantly increased greenhouse gas concentrations, leading to rapid and ongoing climate warming.
The key issue with anthropogenic climate change is not just the absolute temperature values, but the speed at which temperatures are rising. The changes we are observing today are occurring over decades, not over hundreds, thousands, or millions of years. If emissions continue unabated, temperatures are projected to rise by 2-4°C by the end of the century.
On the other hand, one could argue that in the past, if a forest caught fire, there was no way to extinguish it, so it could burn an enormous area, possibly even the size of a country or continent, until it naturally extinguished. Does this not counterbalance the current burning of fossil fuels?
The impacts of such fires and the effects of current anthropogenic greenhouse gas emissions differ significantly in terms of scale, frequency, and duration of their influence on the climate.
Natural Fires:
Short-Term Effects: Natural fires release CO₂, methane, and other gases into the atmosphere, which can temporarily increase temperatures and alter atmospheric composition.
Carbon Recycling: Burned forests can absorb CO₂ as they regenerate, mitigating the long-term impact of fires on the atmosphere. Historically, this process was natural, but now deforestation and burning prevent forests from regenerating.
Natural Emission Rates: While large natural fires can have significant local impacts, on a planetary scale, natural CO₂ emissions from fires are part of the natural carbon cycle.
Human Emissions:
Continuous Emissions: Human activities, such as fossil fuel burning and deforestation, continuously release CO₂ in large quantities. This disrupts the natural carbon cycle, leading to increased greenhouse gas concentrations.
Cumulative Impact: Human emissions have a cumulative impact, raising greenhouse gas concentrations in the atmosphere over the long term.
Industrial Scale: The amount of CO₂ released from human activities far exceeds emissions from natural local fires. For example, the annual global CO₂ emissions from fossil fuel combustion and industrial activities amount to billions of tons.
The key issue is that human combustion occurs almost everywhere on land, unlike natural processes in the past.
Let's now look at the general factors that affect a planet's climate:
Solar Radiation and Galactic Influences
Solar Radiation: Solar radiation does indeed vary through natural cycles, such as the 11-year solar sunspot cycle and long-term changes in solar activity. Changes in solar activity, like sunspot cycles, can influence climate over decades or centuries. However, measurements show that recent increases in temperature cannot be attributed to changes in solar radiation.
Position in the Galaxy: The solar system moves through the galaxy and passes through regions with varying densities of stars and interstellar medium. These changes might affect climate over geological time scales of millions of years, but they do not explain the rapid climate changes observed in recent decades.
Cosmic Radiation: Cosmic radiation may influence cloud formation and, consequently, climate. However, this effect is relatively small compared to the impacts of greenhouse gases.
Natural Climate Variability
Natural Climate Cycles:
1.Volcanic Activity: Large volcanic eruptions can influence the climate in the short term by causing cooling due to the aerosols they emit. Over geological timescales, prolonged volcanic activity can increase CO2 concentrations and lead to warming.
2. Geological Processes: The movement of continents affects ocean currents and weather patterns. At the beginning of the Cretaceous and early Triassic periods, continents were in very different positions compared to today, affecting the climate balance due to differences in land-sea distribution.
3. Astronomical Cycles (Milankovitch Cycles):
Eccentricity: Changes in the shape of Earth’s orbit around the Sun.
Axial Tilt: Changes in the tilt of Earth's axis.
Precession: Changes in the direction of Earth's rotational axis.
Milankovitch cycles suggest that we should be approaching a new glacial period within the next several tens of thousands of years, given that the last ice age ended around 11,700 years ago. However, this natural tendency may have been delayed due to human factors.
4. Ocean Currents:
Changes in ocean current flow can affect the distribution of heat on the planet, causing cooling or warming.
5. Tectonic Movements:
Movements of the continents can alter the distribution of oceans and landmasses, affecting ocean currents and climate.
6. Atmospheric Composition:
Changes in the concentration of greenhouse gases, such as carbon dioxide and methane, can significantly impact global temperatures.
Recent climate changes may indeed be part of a larger natural cycle. The Earth goes through periods of natural warming and cooling related to the aforementioned factors.
Of course, human activity has certainly impacted the environment, but it is useful to view this impact within the context of a natural framework of change. Natural mechanisms can also cause significant climate changes. Our planet is filled with complex natural systems that interact in ways we cannot always fully understand.
I do not want to undermine our responsibility as humans, but it is worth remembering that our planet has a long history of natural changes, and human activity is just one part of this complex puzzle. The combination of natural and anthropogenic factors may give us a more complete picture of the challenges we face.
Let’s keep an open mind and examine all possible causes so that we can find the best solutions for managing our environmental issues. Thank you for reading, and I hope this perspective has provided you with some new insights!
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