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.