Last Year Was Earth’s Warmest Year On Record Since 1880
2023 has set the record for 'Earth’s warmest year since 1880,' according to NASA's Goddard Space Flight Center. Learn more about why that matters here.
Credit; NASA's Goddard Space Flight Center
Credit; NASA's Goddard Space Flight Center
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00:002023 was the hottest year on record by a large margin. But why does NASA, a space agency,
00:10even look at Earth's temperature record?
00:27Let's start from the beginning. NASA's Goddard Institute for Space Studies, or GIS, creates
00:34its global temperature record using land and ocean surface data collected from thousands
00:38of instruments and buoys around the world. But this critical dataset of Earth's temperature
00:43has an origin story that starts 100 million miles away, on planet Venus.
00:51It's 900 degrees hot at the surface, has powerful high altitude winds, and is blanketed by a
00:57dense carbon dioxide atmosphere.
00:59The Goddard Institute for Space Studies here in New York was set up in the early 1960s
01:04to provide a connection between NASA and the academic community. And so it was very much
01:10an ideas shop, and so we spent a lot of time with, you know, the formation of galaxies
01:15and black holes and planetary program and Voyager. And we were involved very early on
01:21in some of the missions to Venus and Jupiter.
01:25Back then, when GIS researchers were studying the weather on Venus, scientists noticed something
01:29fascinating. A thick atmosphere made up of clouds and carbon dioxide was trapping heat.
01:35So much heat that Venus had a surface hot enough to melt lead. This trapping of heat
01:40is known as the greenhouse gas effect. One of the lead Venus researchers at GIS, Dr.
01:45James Hansen, realized that greenhouse gases were also building up in Earth's atmosphere.
01:51So he switched his sights to his home planet and pledged to model the changing atmosphere
01:55of Earth. And to verify or ground truth his model, he needed real-world measurements
01:59over time. So he began keeping track of Earth's global temperature record, dating back to
02:051880, when there was a sufficient amount of data to pull from.
02:09We used our expertise in understanding literally the clouds of Venus and the clouds and dynamics
02:18of Jupiter, and then we took that and we started to think about how you would do the same thing
02:24for the Earth. Since then, GIS has kept its sights on the
02:27global temperature record. And that was the birth of GIS as a climate
02:33modeling institution. And scientists have seen a clear trend in
02:37that record, rising temperatures. And they know why.
02:42The key difference between, say, this decade and the decade before and the decade before
02:47that is that the temperatures have been rising because of our activities, because of principally
02:54the burning of fossil fuels. Without the presence of humans, Earth's temperature
03:03would rise and fall due to a complex array of natural drivers.
03:07With human presence, however, the temperature just continues to rise.
03:11We know that by observing temperature anomalies. Measuring temperature anomalies means that
03:17we look at the change over time rather than absolute temperatures.
03:22The data map you see here isn't showing that the Arctic saw warmer temperatures than the
03:26tropics. It's saying the Arctic was that much warmer
03:29than the Arctic has been in previous years, which is an anomaly in Arctic temperatures.
03:35But how do we get those anomaly measurements?
03:37Let's say you want to track if apples these days are generally larger, smaller, or the
03:44same size as they were 20 years ago. In other words, you want to track the change
03:49over time. Imagine each person on your apple measuring
03:52team has their own food scale. Person A measures apple 1, and their food
03:57scale reads 6 ounces. Person B measures the same apple, but their
04:01scale reads 7 ounces. Since these scales are calibrated differently,
04:06your team ended up with two different recorded weights for the same exact apple.
04:11There's some imprecision in the measurements. And to account for that, when you compare
04:14this apple's measurement to the apples growing next year, you'll need to look at their difference
04:18rather than absolute weights, focusing on the anomaly, or how much heavier or lighter
04:23the next apple is from year to year. So for temperatures, while it would be great
04:29to have the same exact scale or thermometer all over the world measuring the temperature
04:33in the same exact way, we don't. Instead, we focus on how much warmer or colder the
04:38temperatures are in each place based on their own instruments.
04:43Another factor to consider is since you're tracking apples from all over the globe, there
04:47are differences in baseline weights. Let's say apples grown in Florida are generally
04:51larger than apples grown in Alaska. Like in real life, how Floridian temperatures
04:56are generally much higher than Alaskan temperatures. So how do you track the change in apple sizes
05:01from apples grown all over the world while still accounting for their different baseline
05:05weights? By focusing on the difference within each area rather than the absolute weights.
05:12So when it comes to the temperature record, scientists aren't comparing temperatures
05:16in Bermuda to temperatures in Greenland and averaging them together for net warming. Instead,
05:21we're comparing the change in temperatures in Bermuda to the change in temperatures in
05:26Greenland. Again, we look at the anomaly measurements to track the change over time. Now let's scale
05:32this example up.
05:33If you have a weather station, let's say here in New York City, and you compare it
05:38to a weather station in Washington DC or Montreal, they tell very different stories about the
05:44absolute temperature, right? So Montreal is colder and Washington DC is often warmer.
05:50But when they move up and down, when there's a month that is warmer or colder, it's basically
05:55the same in all three locations. And so by looking at the anomalies, how much warmer
06:00it is than normal for that particular point, and then you look at those anomalies at all
06:06those different points and you can average those, it turns out that you can fill out
06:11the gaps much more effectively.
06:15As you can see, this big picture global temperature is comprised of much smaller concentrated
06:21data points from all over the world. So while globally temperatures averaged out to be record
06:26hot, it wasn't record hot in every single location around the world. But why did 2023
06:32see record heat? Well, to put it simply, a combination of high greenhouse gas emissions
06:38and the transition out of three consecutive years of La Nina conditions and into El Nino
06:43conditions led to record breaking heat. But the year was in some respects still surprisingly
06:48hot and NASA is continuing its research on why. Typically, the largest cause of short
06:55term year to year differences in temperature is usually La Nina and El Nino weather patterns.
07:00La Nina generally cools things down while El Nino warms them up. The largest cause of
07:05long term decade by decade differences in temperature is greenhouse gas emissions and
07:10the subsequent trapped heat by greenhouse gases. So while we don't expect every year
07:15to be a new record like 2023, we do expect new records as long as we continue to increase
07:21greenhouse gas emissions. The key thing to take away from all of this is that the long
07:29term trends are pretty much relentlessly up. We're going to continue to have records be
07:37broken because that baseline is moving all the time. And then the weather is sitting
07:43on top of that. And so when the weather is warmer than normal, then we're going to get
07:48these records. But even when it's cooler than normal, we don't go back to what it was.
07:58Hopefully we've answered some of your questions surrounding 2023's noteworthy temperature
08:02record. But you might be left wondering what we're doing about it. NASA is your space agency
08:08when it comes to powering solutions. We're helping other agencies and groups with efforts
08:13to reduce future warming. Clean solar and wind power is being planned using modeling
08:18from NASA Goddard's Mara and NASA Langley's Power. NASA is also developing green aviation
08:25that aims to make air travel more sustainable through new flight technology. And we're also
08:30helping people adapt to climate change challenges that are already here through programs like
08:35Open ET, helping water management across the Western U.S. And Black Marble, which uses
08:41nightlight data to provide critical information to first responders after hurricanes and other
08:46hazards and disasters.