The Earth is heating up faster than ever before — 2024 was the hottest year on record, with the last decade recorded to have been the warmest in modern history, according to recent NASA estimates. In fact, each of the last four decades has been hotter than the one before it, going back to 1850.
Earth’s Temperature Is Rising
The frightening trend, according to reports, is caused mainly by human activity, notably the emission of greenhouse gases that retain heat in our atmosphere. The report of the 2023 Intergovernmental Panel on Climate Change (IPCC) quoted by the US space agency attributed the emissions to the heat waves, wildfires, heavy rain and coastal flooding.
Gavin Schmidt, head of NASA’s Goddard Institute for Space Studies (GISS), commented, “The key thing to take away from all of this is that the long-term trends are pretty much relentlessly up.”
How Scientists Gather Data
In order to monitor the temperature of Earth, researchers collect information from land and ocean sources across the world. On land, there are tens of thousands of weather stations measuring air temperature every day, while ships and buoys are deployed for the measurement of sea surface temperature.
However, global temperature isn’t calculated using just a simple average of these numbers. Instead, researchers calculate “temperature anomalies”, effectively meaning how much the temperature deviates from a “normal” baseline, which the climate and space agency defines as the average from 1951 to 1980.
Nathan Lenssen, a climate scientist involved in the process work, explained, “When it’s two degrees warmer than normal in Denver, it’s going to be two degrees warmer than normal at the top of Bear Peak.” This consistency across nearby locations, scientists say, helps fill in gaps where weather stations are sparse, for example: in deserts and(or) polar regions.
Adjusting for Urban Heat and Station Spacing
Urban areas, on the other hand, tend to be warmer than rural ones due to concrete, asphalt, and heat generated by vehicles and factories, in a phenomenon commonly known as the “urban heat island” effect. According to NASA, scientists carefully adjust for this in order to avoid skewing global averages.
Given that the impact of these urban heat islands has “a minuscule effect on global temperature”, estimated to be about “100th of a degree”, Lenssen explained that in order ensure accuracy, temperature readings from cities and airports are often excluded.
Meanwhile, the temperature stations are often spaced out in an uneven manner, but because temperature anomalies remain consistent over hundreds of miles, scientists can estimate values in less-monitored regions, in turn effectively weighing nearby data more rigorously.
Different Records, Same Story
Additionally, Europe’s Copernicus Climate Change Center — NOAA, Berkeley Earth, and Britain’s Met Office all maintain temperature records.
These records are backed by natural evidence including tree rings, ice cores, and coral, all of which collectively serve as a confirmation of Earth getting warming faster now than in at least the past 2,000 years.
“When we say what’s happening now is special, we’re not just saying that because it’s happening to us,” Schmidt stressed.
Why Temperatures Fluctuate
Climate experts say that yearly temperatures fluctuate because of climate patterns like El Nino and La Nina, both of which are reported to cause temporary warming or cooling effects. Volcanic eruptions and changes in air pollution also play a role.
However, Schmidt insists that these factors don’t change the overall warming trend as “a strong El Nino that began in spring 2023 likely contributed to the soaring temperatures that year, but the global heat surge continued well after El Nino abated.”
Why 1.5 Degrees Celsius Is the Key
In recent years, a great deal of focus has seemingly shifted toward our planet reaching 1.5 degrees Celsius above pre-industrial temperatures. This threshold is important because the 2015 Paris Agreement aims to limit warming to this level in a bid to reduce climate-related risks.
NASA’s data shows 2024 was about 1.47 degrees Celsius above pre-industrial levels, with some months exceeding 1.5 degrees Celsius. “Every 10th of a degree counts… the impacts of 1.6 are going to be worse than the impacts of 1.5,” Schmidt warned, while also adding that it’s still worrying because “we’re seeing the impacts already, and this is what’s going to keep happening until we reduce emissions.”
Why a Degree or Two of Warming Is Big Deal
Though daily weather can swing widely, a global temperature change of just one to two degrees is just as huge as it takes enormous energy to warm the whole planet’s oceans, land, and atmosphere.
To put things in perspective, Schmidt pointed to the Pliocene epoch 2.5 million years ago, when Earth was reportedly three degrees Celsius warmer and ice sheets shrank even as sea levels rose by dozens of feet. “And now we’ve warmed by 1.5 degrees. We are halfway Pliocene-level warmth in just 150 years.”
NASA’s Global Temperature Record
The American space agency’s temperature tracking started in the early 1980s, led by James Hansen, who is believed to have shifted focus from Venus to Earth after realising the dangers of rising greenhouse gases. The first temperature record was published in 1981, and since then, the method has been refined by a team led by Reto Ruedy.
(With inputs from NASA’s Earth Science)
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