A New Climate Reality

Recent studies indicate that Earth has transitioned into a new climate state that hasn't been observed for over 100,000 years. Currently, the planet is more than 1 degree Celsius (1.8 degrees Fahrenheit) warmer than it was prior to industrialization, and levels of greenhouse gases in the atmosphere are sufficient to keep temperatures elevated for the foreseeable future.

Even under the most favorable scenarios—where humanity ceases the combustion of fossil fuels and curtails other greenhouse gas emissions—average global temperatures are likely to remain at least 1°C above preindustrial levels, if not significantly higher, for centuries to come. This new climate state, characterized by persistent warming of 1°C or more, allows for comparisons with temperature reconstructions from the distant past.

Estimating Historical Temperatures

To piece together temperature data from eras lacking thermometers, paleoclimate scientists utilize various natural archives. The most comprehensive records, spanning thousands of years, are found in sediment layers at the bottoms of lakes and oceans. These layers contain biological, chemical, and physical evidence that offers insights into past climates. Researchers analyze sediment cores extracted from these sites to gather information.

While these sediment records are invaluable, they come with notable limitations. Factors such as bottom currents and burrowing organisms can disrupt the sediment, obscuring short-term temperature variations. Moreover, the timelines for these records are not precisely defined, so averaging multiple records can smooth over fine-scale fluctuations, prompting scientists to be cautious when comparing long-term temperature records with short-term extremes.

Reflecting on Thousands of Years

The Earth's average global temperature has oscillated between glacial and interglacial periods in cycles lasting roughly 100,000 years. These cycles are influenced by gradual, predictable shifts in Earth's orbit that affect greenhouse gas levels in the atmosphere.

Currently, we find ourselves in an interglacial period that started approximately 12,000 years ago as ice sheets retreated and greenhouse gases increased. During this interglacial phase, global temperatures may have peaked around 6,000 years ago, yet they likely did not surpass the 1°C warming threshold, according to the Intergovernmental Panel on Climate Change (IPCC).

Another study indicates that global temperatures have continued to rise throughout the interglacial period, an area that remains subject to ongoing research. To find a time comparable to today's warmth, we must look even further back. The last glacial phase extended nearly 100,000 years, and there is no evidence suggesting that long-term global temperatures ever reached the preindustrial baseline during that span.

Digging Deeper into the Past

Looking back to the previous interglacial period, which peaked around 125,000 years ago, we do encounter evidence of warmer conditions. Research suggests that the long-term average temperature was likely no more than 1.5°C (2.7°F) above preindustrial levels—just slightly higher than our current global warming state.

What Lies Ahead?

If substantial and sustained reductions in greenhouse gas emissions do not occur, the Earth is on a trajectory to experience temperatures approximately 3°C (5.4°F) above preindustrial levels by the century's end, potentially even exceeding this figure. In such a scenario, we would need to look back millions of years to find a climate state with temperatures as elevated as those projected.

This would lead us back to the Pliocene epoch, a time when Earth's climate was vastly different from the conditions that enabled the rise of agriculture and civilization.

The first video titled "One Million Years into Climate Change's Past" delves into the historical climate shifts and their implications for our current situation.

The second video, "Is Global Warming Speeding Up?" explores the acceleration of global warming and its potential consequences for the future.