Climate models serve as a base for sound policy and decision-making around climate action. And the best way to increase their accuracy is to simulate past climates using them and see if they agree with geological evidence.
So, do the model simulations so far agree with the climate imprints on our planet? Not really! Global temperature reconstructions for approximately 12,000 years ago have generated contrasting trends. In short, the two significant lines of evidence — climate models and geological records — point climate science in opposite directions.
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The recently published review article addresses this conflict between computer models and our planet’s records. And in doing so offers a potential answer to the question in the title!
Historical global temperature conundrum
Model reconstructions suggest an increase in global average temperatures in the last 6,500 years. On the other hand, paleo-environmental “proxy” data, which includes evidence from oceans, lakes, and other natural archives, point to a peak global average temperature about 6,500 years ago, followed by a global cooling trend until humans started burning fossil fuels.
The scientific community refers to this as the Holocene global temperature conundrum, where the Holocene refers to the last 11,700 years of the Earth’s history when the temperatures remained relatively stable.
So, there are two possible conclusions: if the proxy data are correct, it implies that our climate model projections are underestimating the true extent of the potential impact of global warming. And if the model simulations are correct, we must refine the tools that analyse our natural archives.
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Using the wide swathe of data from the past 12,000 years, lead author Dr Darrel Kaufmann and postdoctoral researcher Ellie Broadmann conducted a comprehensive assessment. Their study reveals that about 6,500 years ago, global temperatures were likely warmer. Then a cooling trend followed till the 1800s when the industrial revolution and anthropogenic activities started to induce warming.
However, there could be more to this puzzle than we can see, and the researchers caution that this study should not be construed as the final word.
Significance of understanding Earth’s temperature tantrums
Climate models are a crucial source of detailed quantitative climate predictions, so their accuracy is critical to prep ourselves for the looming climate catastrophe. Also, tracing the changes in global average temperatures is essential to gauge the extent of human impact on the planet’s fever. It is the primary metric that brings world leaders to the discussion table at climate conferences.
The researchers suggest that whether these numbers trend up or down, the changes in the past 6,500 years have been gradual— probably less than 1°C. This is a tiny speck compared to the amount of warming already measured in the last 100 years, most of which has been due to anthropogenic drivers.
Yet, our efforts to tackle this crisis has been pretty lacklustre so far, as evident in the recent COP26!
Is the conundrum solved?
As the next step, researchers are trying to retrace our steps based on a comprehensive global-scale assessment, showing that we haven’t yet cracked this riddle.
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“In particular, our review revealed how surprisingly little we know about slow-moving climate variability, including forces now set into motion by humans that will play out as sea level rises and permafrost thaws over coming millennia, ” says Dr Kaufmann
But, it is still essential that we understand the past patterns of our climate system and set benchmarks that aid with robust and improved forecasts for future climate, especially in light of continued warnings about our planet’s warming.
In fact, Dr Kaufman’s lab is testing new methods which involve employing amino acids preserved in lake sediments and newly developed radiocarbon dating techniques to sharpen our understanding of proxy data from Earth. While this uphill journey is complex and challenging, “more research is needed to firmly resolve this conundrum,” concludes Dr Kaufman.
The study was published in the reputed journal Nature last month and can be accessed here.
NOTE – This article was originally published in weather and can be viewed here
Tags: #climate, #climatechange, #climatecrisis, #cooling, #earth, #environment, #getgreengetgrowing, #globalwarming, #gngagritech, #greenstories, #oceans, #planets
