Last week an article in the Guardian by John Abraham reported on how pollen data indicates a reversal natural global cooling. Over the last 11,000 years, humans have reversed a natural trend toward slightly cooler temperatures into the opposite trend, with slowly warming temperatures in the last 2,000 years, especially in the last century, which has seen warmer temperatures than in almost any of the previous 11,000 years. Scientists from the University of Wyoming just published the results of their research in the journal Nature. They measured the distribution of pollen from plants to determine what plants thrived where and when. Because each type of plant produces pollen only within a narrow temperature range, and because pollen doesn’t degrade for thousands of years, the scientists could determine ancient temperatures accurately. Focusing on the Holocene period that began about 11,000 years ago, they detected a slight cooling trend for the first 2,000 years, which has since reversed. Temperatures since then have trended warmer, with a noticeable bump over the last 2,000 years as man entered the industrial age and began burning lots of coal. A spike over the last century or so has produced higher temperatures than in almost any year over the last 11,000.
Temperature in North America and Europe over the past 11,000 years based on pollen reconstruction data. Illustration: Marsicek et al. (2018), Nature.
The significance of the research is that climate does fluctuate naturally over time, but human activity now dominates and drives changes in temperature beyond any recent historical experience. Consequences include sea level rise, increased rainfall, heat waves, and droughts. Mankind must sharply slow or stop its production of the heat-trapping gases that result from burning carbon-based fossil fuels, which are forcing the higher temperatures beyond those that humans and the Earth have known for thousands of years, to the point that it’s continued hospitality for human life and indeed the sustainability of all life on the planet is now threatened. We don’t have much time. We must act now.