Environmental Note: Climate Change And Where This Is All Going

During the Paleocene-Eocene Thermal Maximum (PETM), the environmental changes occurred rapidly on a geological timescale, but the exact rate of change varied depending on the location and the specific environmental aspect being considered.

The onset of the PETM, marked by the carbon isotope excursion (CIE), occurred over a relatively short period of about 20,000 years. This rapid onset suggests that the release of carbon into the atmosphere and the subsequent warming happened quickly, leading to swift environmental changes.

Some of the rapid environmental changes during the PETM include:

1. Temperature increase: Global surface temperatures rose by 5-8°C (9-14°F) over a period of a few thousand years, which is considered very rapid in geological terms.

2. Hydrological changes: The warming led to an intensified hydrological cycle, with increased precipitation and weathering rates occurring over a relatively short period.

3. Ocean acidification: As the oceans absorbed more atmospheric CO2, the pH of seawater decreased, leading to rapid ocean acidification.

4. Biotic response: Many species experienced range shifts, evolutionary changes, and extinctions in response to the rapidly changing environmental conditions. These biotic responses occurred over thousands to tens of thousands of years.

It is important to note that while the PETM warming was rapid on a geological timescale, it still occurred over thousands of years. In contrast, the current anthropogenic climate change is happening at an even faster rate, with significant changes observed over decades to centuries. This highlights the unprecedented nature of the current climate change and the challenges it poses for species adaptation and ecosystem resilience.


The carbon isotope excursion (CIE) during the Paleocene-Eocene Thermal Maximum (PETM) and the ongoing anthropogenic climate change since the Industrial Revolution share some similarities in terms of their impact on the global carbon cycle and climate. However, there are also important differences between the two events.

Similarities:
1. Carbon release: Both the PETM and the current anthropogenic climate change are characterized by a significant release of carbon into the atmosphere. During the PETM, a massive amount of light carbon (12C) was released, while the Industrial Revolution marked the beginning of large-scale anthropogenic CO2 emissions from the burning of fossil fuels.

2. Greenhouse effect: The carbon release during both events led to an increased greenhouse effect, causing global temperatures to rise. The PETM saw a global temperature increase of 5-8°C (9-14°F), while the Earth has experienced a temperature rise of approximately 1°C (1.8°F) since the pre-industrial era.
3. Ocean acidification: In both cases, the increased atmospheric CO2 concentrations led to increased absorption of CO2 by the oceans, resulting in ocean acidification.

Differences:
1. Source of carbon: The source of the carbon released during the PETM is still debated, with hypotheses including methane hydrates, volcanic activity, or permafrost thawing. In contrast, the primary source of carbon emissions during the current anthropogenic climate change is the burning of fossil fuels.

2. Rate of change: Although the PETM CIE and warming were rapid on a geological timescale, occurring over thousands of years, the current rate of change is even faster. The anthropogenic carbon release and the resulting climate changes are occurring over decades to centuries, making it more challenging for species and ecosystems to adapt.

3. Background conditions: The Earth's climate and ecosystems during the PETM were different from today. The PETM occurred during a time of already warm global temperatures, whereas the current climate change is occurring from a cooler baseline.

4. Magnitude of change: The amount of carbon released during the PETM is estimated to be around 2,000 to 7,000 gigatons of carbon (GtC). If anthropogenic emissions continue unabated, the total carbon release could potentially surpass that of the PETM in the coming centuries.

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Highlights

1. The PETM experienced a larger total temperature increase (5-8°C) compared to the current warming (~1°C), but the PETM warming occurred over a much longer timescale (~20,000 years).

2. The rate of temperature change during the current anthropogenic climate change is significantly faster than during the PETM. The PETM warming rate was approximately 0.025-0.04°C per century, while the current rate (since 1970) is around 0.6-0.7°C per century.

3. The PETM saw a larger total increase in atmospheric CO2 levels (~900-1,600 ppm) compared to the current increase (~145 ppm). However, the current CO2 increase has occurred over a much shorter time.

4. The rate of CO2 change during the current anthropogenic climate change is much faster than during the PETM. The PETM CO2 increase was approximately 45-80 ppm per thousand years, while the current rate (since 1960) is around 2.4 ppm per year.

5. There is insufficient data to reliably compare the rate of rate of CO2 change between the two events. However, the rate of CO2 increase has been accelerating during the anthropogenic climate change, increasing from ~0.6 ppm per year (1850-1950) to ~2.4 ppm per year (since 1960).

This comparison underscores the unprecedented rate of change in both temperature and atmospheric CO2 levels during the current anthropogenic climate change compared to the PETM, despite the larger total changes observed during the PETM.


The Paleocene-Eocene Thermal Maximum (PETM) and the current anthropogenic climate change are two periods marked by significant global warming and changes in the Earth's climate system. However, there are notable differences in the magnitude and rate of these changes.

During the PETM, global temperatures increased by 5-8°C (9-14°F) over approximately 20,000 years. This warming was caused by a massive release of carbon into the atmosphere, which led to an increase in atmospheric CO2 levels by around 900-1,600 ppm. The rate of temperature change during the PETM was approximately 0.025-0.04°C (0.045-0.072°F) per century, and the rate of CO2 increase was around 45-80 ppm per thousand years.

In contrast, the current anthropogenic climate change has seen a temperature increase of approximately 1°C (1.8°F) since the pre-industrial era (1850-1900). Although the total temperature increase is smaller compared to the PETM, the rate of change is significantly faster. Since 1970, the rate of temperature change has been around 0.6-0.7°C (1.08-1.26°F) per century, which is more than 15 times faster than the warming rate during the PETM.

Similarly, the increase in atmospheric CO2 levels during the current climate change is smaller in total magnitude (~145 ppm, from ~280 ppm to 425 ppm) compared to the PETM. However, this increase has occurred over a much shorter timeframe, with a rate of CO2 change of approximately 2.4 ppm per year since 1960. This rate is more than 100 times faster than the CO2 increase during the PETM.

Furthermore, the rate of CO2 increase has been accelerating during the current anthropogenic climate change. Between 1850 and 1950, the rate of CO2 increase was around 0.6 ppm per year, but since 1960, it has increased to approximately 2.4 ppm per year. This acceleration in the rate of change is a concerning aspect of the current climate change, as it may limit the ability of Earth's systems and species to adapt to the rapidly changing conditions.

In summary, while the PETM saw larger total changes in temperature and atmospheric CO2 levels, the current anthropogenic climate change is characterized by significantly faster rates of change. This unprecedented rate of change highlights the urgent need for action to mitigate greenhouse gas emissions and adapt to the ongoing and future impacts of climate change on Earth's systems and species.