El Niño - Blog Posts

Six Answers to Questions You’re Too Embarrassed to Ask about the Hottest Year on Record

You may have seen the news that 2023 was the hottest year in NASA’s record, continuing a trend of warming global temperatures. But have you ever wondered what in the world that actually means and how we know?

We talked to some of our climate scientists to get clarity on what a temperature record is, what happened in 2023, and what we can expect to happen in the future… so you don’t have to!

1. Why was 2023 the warmest year on record?

The short answer: Human activities. The release of greenhouse gases like carbon dioxide and methane into the atmosphere trap more heat near Earth’s surface, raising global temperatures. This is responsible for the decades-long warming trend we’re living through.

But this year’s record wasn’t just because of human activities. The last few years, we’ve been experiencing the cooler phase of a natural pattern of Pacific Ocean temperatures called the El Niño Southern Oscillation (ENSO). This phase, known as La Niña, tends to cool temperatures slightly around the world. In mid-2023, we started to shift into the warmer phase, known as El Niño. The shift ENSO brought, combined with overall human-driven warming and other factors we’re continuing to study, pushed 2023 to a new record high temperature.

2. So will every year be a record now?

Almost certainly not. Although the overall trend in annual temperatures is warmer, there’s some year-to-year variation, like ENSO we mentioned above.

Think about Texas and Minnesota. On the whole, Texas is warmer than Minnesota. But some days, stormy weather could bring cooler temperatures to Texas while Minnesota is suffering through a local heat wave. On those days, the weather in Minnesota could be warmer than the weather in Texas. That doesn’t mean Minnesota is warmer than Texas overall; we’re just experiencing a little short-term variation.

Something similar happens with global annual temperatures. The globe will naturally shift back to La Niña in the next few years, bringing a slight cooling effect. Because of human carbon emissions, current La Niña years will be warmer than La Niña years were in the past, but they’ll likely still be cooler than current El Niño years.

3. What do we mean by “on record”?

Technically, NASA’s global temperature record starts in 1880. NASA didn’t exist back then, but temperature data were being collected by sailing ships, weather stations, and scientists in enough places around the world to reconstruct a global average temperature. We use those data and our modern techniques to calculate the average.

We start in 1880, because that’s when thermometers and other instruments became technologically advanced and widespread enough to reliably measure and calculate a global average. Today, we make those calculations based on millions of measurements taken from weather stations and Antarctic research stations on land, and ships and ocean buoys at sea. So, we can confidently say 2023 is the warmest year in the last century and a half.

However, we actually have a really good idea of what global climate looked like for tens of thousands of years before 1880, relying on other, indirect ways of measuring temperature. We can look at tree rings or cores drilled from ice sheets to reconstruct Earth’s more ancient climate. These measurements affirm that current warming on Earth is happening at an unprecedented speed.

4. Why does a space agency keep a record of Earth’s temperature?

It’s literally our job! When NASA was formed in 1958, our original charter called for “the expansion of human knowledge of phenomena in the atmosphere and space.” Our very first space missions uncovered surprises about Earth, and we’ve been using the vantage point of space to study our home planet ever since. Right now, we have a fleet of more than 20 spacecraft monitoring Earth and its systems.

Why we created our specific surface temperature record – known as GISTEMP – actually starts about 25 million miles away on the planet Venus. In the 1960s and 70s, researchers discovered that a thick atmosphere of clouds and carbon dioxide was responsible for Venus’ scorchingly hot temperatures.

Dr. James Hansen was a scientist at the Goddard Institute for Space Studies in New York, studying Venus. He realized that the greenhouse effect cooking Venus’ surface could happen on Earth, too, especially as human activities were pumping carbon dioxide into our atmosphere.

He started creating computer models to see what would happen to Earth’s climate as more carbon dioxide entered the atmosphere. As he did, he needed a way to check his models – a record of temperatures at Earth’s surface over time, to see if the planet was indeed warming along with increased atmospheric carbon. It was, and is, and NASA’s temperature record was born.

5. If last year was record hot, why wasn’t it very hot where I live?

The temperature record is a global average, so not everywhere on Earth experienced record heat. Local differences in weather patterns can influence individual locations to be hotter or colder than the globe overall, but when we average it out, 2023 was the hottest year.

Just because you didn’t feel record heat this year, doesn’t mean you didn’t experience the effects of a warming climate. 2023 saw a busy Atlantic hurricane season, low Arctic sea ice, raging wildfires in Canada, heat waves in the U.S. and Australia, and more.

And these effects don’t stay in one place. For example, unusually hot and intense fires in Canada sent smoke swirling across the entire North American continent, triggering some of the worst air quality in decades in many American cities. Melting ice at Earth’s poles drives rising sea levels on coasts thousands of miles away.

6. Speaking of which, why is the Arctic – one of the coldest places on Earth – red on this temperature map?

Our global temperature record doesn’t actually track absolute temperatures. Instead, we track temperature anomalies, which are basically just deviations from the norm. Our baseline is an average of the temperatures from 1951-1980, and we compare how much Earth’s temperature has changed since then. 

Why focus on anomalies, rather than absolutes? Let’s say you want to track if apples these days are generally larger, smaller, or the same size as they were 20 years ago. In other words, you want to track the change over time.

Apples grown in Florida are generally larger than apples grown in Alaska. Like, in real life, how Floridian temperatures are generally much higher than Alaskan temperatures. So how do you track the change in apple sizes from apples grown all over the world while still accounting for their different baseline weights? 

By focusing on the difference within each area rather than the absolute weights. So in our map, the Arctic isn’t red because it’s hotter than Bermuda. It’s red because it’s gotten relatively much warmer than Bermuda has in the same time frame.

Want to learn more about climate change? Dig into the data at climate.nasa.gov.

Make sure to follow us on Tumblr for your regular dose of space!

Six Answers to Questions You’re Too Embarrassed to Ask about the Hottest Year on Record

You may have seen the news that 2023 was the hottest year in NASA’s record, continuing a trend of warming global temperatures. But have you ever wondered what in the world that actually means and how we know?

We talked to some of our climate scientists to get clarity on what a temperature record is, what happened in 2023, and what we can expect to happen in the future… so you don’t have to!

1. Why was 2023 the warmest year on record?

The short answer: Human activities. The release of greenhouse gases like carbon dioxide and methane into the atmosphere trap more heat near Earth’s surface, raising global temperatures. This is responsible for the decades-long warming trend we’re living through.

But this year’s record wasn’t just because of human activities. The last few years, we’ve been experiencing the cooler phase of a natural pattern of Pacific Ocean temperatures called the El Niño Southern Oscillation (ENSO). This phase, known as La Niña, tends to cool temperatures slightly around the world. In mid-2023, we started to shift into the warmer phase, known as El Niño. The shift ENSO brought, combined with overall human-driven warming and other factors we’re continuing to study, pushed 2023 to a new record high temperature.

2. So will every year be a record now?

Almost certainly not. Although the overall trend in annual temperatures is warmer, there’s some year-to-year variation, like ENSO we mentioned above.

Think about Texas and Minnesota. On the whole, Texas is warmer than Minnesota. But some days, stormy weather could bring cooler temperatures to Texas while Minnesota is suffering through a local heat wave. On those days, the weather in Minnesota could be warmer than the weather in Texas. That doesn’t mean Minnesota is warmer than Texas overall; we’re just experiencing a little short-term variation.

Something similar happens with global annual temperatures. The globe will naturally shift back to La Niña in the next few years, bringing a slight cooling effect. Because of human carbon emissions, current La Niña years will be warmer than La Niña years were in the past, but they’ll likely still be cooler than current El Niño years.

3. What do we mean by “on record”?

Technically, NASA’s global temperature record starts in 1880. NASA didn’t exist back then, but temperature data were being collected by sailing ships, weather stations, and scientists in enough places around the world to reconstruct a global average temperature. We use those data and our modern techniques to calculate the average.

We start in 1880, because that’s when thermometers and other instruments became technologically advanced and widespread enough to reliably measure and calculate a global average. Today, we make those calculations based on millions of measurements taken from weather stations and Antarctic research stations on land, and ships and ocean buoys at sea. So, we can confidently say 2023 is the warmest year in the last century and a half.

However, we actually have a really good idea of what global climate looked like for tens of thousands of years before 1880, relying on other, indirect ways of measuring temperature. We can look at tree rings or cores drilled from ice sheets to reconstruct Earth’s more ancient climate. These measurements affirm that current warming on Earth is happening at an unprecedented speed.

4. Why does a space agency keep a record of Earth’s temperature?

It’s literally our job! When NASA was formed in 1958, our original charter called for “the expansion of human knowledge of phenomena in the atmosphere and space.” Our very first space missions uncovered surprises about Earth, and we’ve been using the vantage point of space to study our home planet ever since. Right now, we have a fleet of more than 20 spacecraft monitoring Earth and its systems.

Why we created our specific surface temperature record – known as GISTEMP – actually starts about 25 million miles away on the planet Venus. In the 1960s and 70s, researchers discovered that a thick atmosphere of clouds and carbon dioxide was responsible for Venus’ scorchingly hot temperatures.

Dr. James Hansen was a scientist at the Goddard Institute for Space Studies in New York, studying Venus. He realized that the greenhouse effect cooking Venus’ surface could happen on Earth, too, especially as human activities were pumping carbon dioxide into our atmosphere.

He started creating computer models to see what would happen to Earth’s climate as more carbon dioxide entered the atmosphere. As he did, he needed a way to check his models – a record of temperatures at Earth’s surface over time, to see if the planet was indeed warming along with increased atmospheric carbon. It was, and is, and NASA’s temperature record was born.

5. If last year was record hot, why wasn’t it very hot where I live?

The temperature record is a global average, so not everywhere on Earth experienced record heat. Local differences in weather patterns can influence individual locations to be hotter or colder than the globe overall, but when we average it out, 2023 was the hottest year.

Just because you didn’t feel record heat this year, doesn’t mean you didn’t experience the effects of a warming climate. 2023 saw a busy Atlantic hurricane season, low Arctic sea ice, raging wildfires in Canada, heat waves in the U.S. and Australia, and more.

And these effects don’t stay in one place. For example, unusually hot and intense fires in Canada sent smoke swirling across the entire North American continent, triggering some of the worst air quality in decades in many American cities. Melting ice at Earth’s poles drives rising sea levels on coasts thousands of miles away.

6. Speaking of which, why is the Arctic – one of the coldest places on Earth – red on this temperature map?

Our global temperature record doesn’t actually track absolute temperatures. Instead, we track temperature anomalies, which are basically just deviations from the norm. Our baseline is an average of the temperatures from 1951-1980, and we compare how much Earth’s temperature has changed since then. 

Why focus on anomalies, rather than absolutes? Let’s say you want to track if apples these days are generally larger, smaller, or the same size as they were 20 years ago. In other words, you want to track the change over time.

Apples grown in Florida are generally larger than apples grown in Alaska. Like, in real life, how Floridian temperatures are generally much higher than Alaskan temperatures. So how do you track the change in apple sizes from apples grown all over the world while still accounting for their different baseline weights? 

By focusing on the difference within each area rather than the absolute weights. So in our map, the Arctic isn’t red because it’s hotter than Bermuda. It’s red because it’s gotten relatively much warmer than Bermuda has in the same time frame.

Want to learn more about climate change? Dig into the data at climate.nasa.gov.

Make sure to follow us on Tumblr for your regular dose of space!

People are forgetting to get gifts. I keep forgetting it's Christmas. I dreamed that it snowed and all was right with the world. Where is my winter weather? Are my brand new snowboots for nothing at all? Do the sno-brums that are perpetually in my parents' cars and at every store mean nothing? Why can I see grass? Are the sleds waiting so patiently in the basement just meaningless hunks of plastic?

Where is MY December??? 😭

Pinpointing the Cause of Earth’s Recent Record CO2 Spike

A new NASA study provides space-based evidence that Earth’s tropical regions were the cause of the largest annual increases in atmospheric carbon dioxide concentration seen in at least 2,000 years.

What was the cause of this?

Scientists suspect that the 2015-2016 El Niño – one of the largest on record – was responsible. El Niño is a cyclical warming pattern of ocean circulation in the Pacific Ocean that affects weather all over the world. Before OCO-2, we didn’t have enough data to understand exactly how El Nino played a part.

Analyzing the first 28 months of data from our Orbiting Carbon Observatory (OCO-2) satellite, researchers conclude that impacts of El Niño-related heat and drought occurring in the tropical regions of South America, Africa and Indonesia were responsible for the record spike in global carbon dioxide.

These three tropical regions released 2.5 gigatons more carbon into the atmosphere than they did in 2011. This extra carbon dioxide explains the difference in atmospheric carbon dioxide growth rates between 2011 and the peak years of 2015-16.

In 2015 and 2016, OCO-2 recorded atmospheric carbon dioxide increases that were 50% larger than the average increase seen in recent years preceding these observations.

In eastern and southern tropical South America, including the Amazon rainforest, severe drought spurred by El Niño made 2015 the driest year in the past 30 years. Temperatures were also higher than normal. These drier and hotter conditions stressed vegetation and reduced photosynthesis, meaning trees and plants absorbed less carbon from the atmosphere. The effect was to increase the net amount of carbon released into the atmosphere.

In contrast, rainfall in tropical Africa was at normal levels, but ecosystems endured hotter-than-normal temperatures. Dead trees and plants decomposed more, resulting in more carbon being released into the atmosphere.

Meanwhile, tropical Asia had the second-driest year in the past 30 years. Its increased carbon release, primarily from Indonesia, was mainly due to increased peat and forest fires -  also measured by satellites.

We knew El Niños were one factor in these variations, but until now we didn’t understand, at the scale of these regions, what the most important processes were. OCO-2’s geographic coverage and data density are allowing us to study each region separately.

Why does the amount of carbon dioxide in our atmosphere matter?

The concentration of carbon dioxide in Earth’s atmosphere is constantly changing. It changes from season to season as plants grow and die, with higher concentrations in the winter and lower amounts in the summer. Annually averaged atmospheric carbon dioxide concentrations have generally increased year over year since the 1800s – the start of the widespread Industrial Revolution. Before then, Earth’s atmosphere naturally contained about 595 gigatons of carbon in the form of carbon dioxide. Currently, that number is 850 gigatons.

Carbon dioxide is a greenhouse gas, which means that it can trap heat. Since greenhouse gas is the principal human-produced driver of climate change, better understanding how it moves through the Earth system at regional scales and how it changes over time are important aspects to monitor.

Get more information about these data HERE.

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