The Earth's warming trend is a hot topic, but new data is stirring up some controversy. How much has our planet really warmed?
Chris Mooney, a Pulitzer Prize-winning journalist and CNN Climate contributor, delves into the complex history of Earth's temperature changes. The story begins with the Industrial Revolution, but the roots go deeper.
Since the end of World War II, planet-warming pollution rates have skyrocketed. But the journey started much earlier with James Watt's steam engine in 1769, and even before that, humans were clearing forests for agriculture, releasing carbon into the atmosphere.
The question of when to mark the 'normal' temperature for Earth is a tricky one. And this is where it gets interesting: a groundbreaking temperature dataset released by UK scientists goes back to 1781, much earlier than the typical 1850 starting point.
But why does this extended timeframe matter? Well, between 1750 and 1850, greenhouse gases increased by 2.5%, causing warming that hasn't been fully accounted for. The new dataset, named GloSAT, suggests the Earth has warmed more than previously calculated.
But here's where it gets controversial: The 1850 start date is a practical choice, but it's not the beginning of industrialization. The new dataset reveals a cooler Earth from 1781 to 1849 compared to 1850-1900, the 'preindustrial' baseline. However, scientists warn that not all warming during this period is due to human activities.
Two massive volcanic eruptions in the early 1800s had a significant cooling effect. These eruptions, including the famous Tambora eruption in 1815, spread particles into the stratosphere, blocking sunlight. Some warming in the late 19th century was a natural recovery from these events, but there's more to the story.
The UN's climate science authority suggests there was likely some human-caused warming between 1750 and 1850, estimated at 0 to 0.2 degrees. The GloSAT scientists agree, and further studies using this dataset and climate models indicate that humans caused 0.09 degrees of warming during this period.
Old temperature records, some dating back to the 17th century, play a crucial role in this research. These records, often collected by early explorers and businesses, help reconstruct global temperatures. For instance, a record in the Bavarian Alps started in 1781 by Augustinian clerics, survived the Napoleonic wars, and shows nearly 3 degrees of regional warming over time.
But how do we piece together the planet's temperature from these local measurements? And what about the oceans, which cover 70% of the Earth? Ships in the 18th century, like the British East India Company, measured temperature, but not as systematically as land-based observations. These records, along with whaling vessel data, contribute to the new dataset, which focuses on marine air temperatures.
The scientists acknowledge the challenges of sparse data in earlier periods, leading to higher uncertainty in temperature estimates. Yet, they confirm that it was undoubtedly cooler before 1850.
So, what does this mean for our understanding of climate change? It's a complex issue. While it might seem concerning that we've underestimated the problem, experts caution against jumping to conclusions. This new data doesn't necessarily undermine climate goals, but it does provide valuable insights into pre-1850 warming.
The finding of earlier warming is significant, but it doesn't accelerate the timeline for climate impacts. It simply adds to the growing evidence of human-induced warming. This additional warming might have contributed to changes in Earth's systems, and it should raise our concern about the mounting impacts of climate change.
In the end, this new dataset is a crucial piece of the puzzle, helping us understand how much we've altered our planet's climate and the potential consequences we face.
