Data Exploration: Direct Impacts of Climate Change
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Data reminder:Direct impacts
Climate change is the long-term heating of the Earth’s climate due to human activities. We’ll explore some of the direct impacts of climate change. These include rising global temperatures and rising sea levels. Other direct impacts include extreme weather, forest fires, drought, and flooding. Later, you will learn how those changes affect society, which we call indirect impacts. For now, let’s focus on one direct impact: sea-level rise.
Rising temperatures in the polar regions can cause ice sheets and glaciers to melt. This sends more water into the oceans. As the water gets warmer, it expands. So, when temperatures rise, sea levels do too.
The long view
Sea levels have gone up and down before. The planet has gone through different cycles of weather. There have been ice ages and warming periods over hundreds of thousands of years. Some people say that the current sea- level rise is part of this cycle. However, scientists have studied coral records and collected layers of sediment from the oceans to learn about the past. They discovered that sea levels have changed little for the last 2,000 years.
In the early 1900s, sea levels suddenly started to climb. From 1900 to 1993, sea levels rose 4 to 5 inches. Between 1993 and 2023, sea levels rose another 4 inches. Chart 1 shows why the trend is so alarming. Sea levels are rising faster. This trend also matches an increase in the burning of fossil fuels by people. Fossil fuels are natural fuels that form over long periods of time. They include oil, natural gas, and coal.
Effect of sea level rise on homes in Summer Haven, Florida. © Getty Images.
Chart 1: Global mean sea level since 1000 CE. By 2° Institute, CC BY-NC 3.0 DEED.
The trend is clearer when we compare the global temperature anomaly with sea-level rise. An anomaly is a change from the norm. Temperature anomaly shows us the increase or decrease from the average temperature. In Chart 2, the temperature anomaly is shown in gray. You can compare it to sea-level rise, shown in blue.
Chart 2: Sea-level changes and changes in global temperature anomaly over the last 1,000 years. From 2° Institute. (To see this view in the interactive chart, you must select “Global Sea Levels” from the top-right menu button and then click the thermometer toggle on the top-left to overlay temperature anomaly). By 2° Institute, CC BY-NC 3.0 DEED.
See? Change
Let’s look at sea levels over the last 150 years. Chart 3 shows sea level data since 1880. How do we know about these changes? From 1880 to 1993, sea-level recordings were collected from different ports worldwide.1 In 1993, NASA started measuring sea levels with satellites. This provided more exact global measurements. NASA is the U.S. space agency.
Scientists began measuring the average increase in sea levels every year. In the 1900s, the average increase was 1.7 millimeters (0.07 inch). By 1993, the rate increased to 2 millimeters (0.08 inch). In 2016, it reached 3.4 millimeters (0.13 inches). By 2022, the yearly rate grew to 4.4 millimeters (0.17 inches). Researchers believe the rate will reach 6.6 millimeters (0.26 inches) by 2050.2 This could cause the sea level along the coastline of the United States to rise as much as 12 inches by 2050. It’s the same increase that happened over the 100 years between 1920 and 2020.3
Chart 3. Sea-level rise, 1880 to 2002. From NOAA. By Our World in Data, CC BY. Explore Chart 3 here.
We’re in over our heads
These might sound like small numbers. After all, 3 millimeters is about the length of a sesame seed. So, what’s the big deal? Well, there are three issues:
- Those small numbers quickly add up. If you stack enough sesame seeds, things get messy quickly.
- Sea levels are rising faster, so those yearly increases will get bigger.
- As shown in Chart 2, it takes a while for sea-level rise to catch up with higher temperatures.
We won’t know what a 1.5- or 2-degree rise in global temperature will mean for sea levels until it happens. The National Oceanic and Atmospheric Administration (NOAA) is a government agency. It researches and protects ocean resources. NOAA says the oceans could rise between 1 and 8 feet (0.4 to 2.4 meters) by 2100 (see Chart 4). That’s a big difference. Scientists think that sea levels will continue to rise, too. How much they rise, however, will depend on how quickly we reduce our greenhouse gas emissions.
Chart 4: This chart shows future sea levels through 2100 for six possible scenarios. These predictions vary based on future rates of greenhouse gas emissions and rise in global temperatures. By climate.gov.
Humanity and the sea
What do the differences in the level of sea rise mean for the world? What does it mean for you and your community? To begin answering those questions, let’s take a look at Map 1, below.
Map 1: Global population density. Courtesy Visual Capitalist.
Can you recognize the shape of the continents from the population density spikes? That’s because most of the global population lives close to the ocean. Take a look at Map 2 below. About 40 percent of the Earth’s population lives within 100 kilometers (about 60 miles) of a coast. Eight of the top 10 largest cities in the world are on a coast.
Map 2. Coastal populations and shoreline degradation. Courtesy PRB.com.
Coastal areas are heavily populated and growing. They are vital for businesses like fishing and tourism. That’s why so many people choose to live near the coast. By 2100, more than 410 million people will be at risk from rising sea levels. Small islands in the Pacific Ocean, such as Kiribati and Tuvalu, could be damaged or destroyed. If sea levels keep rising, flooding and weather events will force some people to move.
Populations will move in and out of new areas. Coastal communities might have dangerous weather events like flooding, hurricanes, and typhoons.
The charts above deal with the average global sea-level rise. However, sea-level changes are different depending on the place. In some areas, the sea-level rise is worse than the global average. So far, we have seen less than a foot of global rising sea levels. However, high-tide flooding is 300 percent to 900 percent more frequent than 50 years ago.4 Coastal communities are already experiencing what climate change can do.
If you live inland, you might think you are safe from rising sea levels. But even people farther from the coast will be affected. They will face the indirect effects of coastal flooding. These changes could be rising costs, mass migration, and food shortages. You will learn more about these changes soon.
Conclusion
Sea-level rise is caused by climate change. Climate change is caused by humans. It threatens coastlines all over the planet and the people who live on it. But sea-level rise will affect all of us, not just those who live on the coast. Climate change and sea-level changes will affect different communities in unequal ways.
As you review this article, think about what people and regions will be most at risk. You might want to explore more about what sea levels will mean for your community or coastal cities around the world. Check out these tools for more:
NOAA Sea Level Rise Viewer: This tool shows how the U.S. coastline will change if sea levels rise between 1 and 10 feet. For some locations — like Fulton Street in Manhattan — you can see a visual estimate of how a place will change based on sea- level increase.
NASA’s IPCC AR6 Sea Level Projection Tool: This tool allows you to see predicted sea levels around the world in different years based on several different warming scenarios.
1 Church, J.A., White, N.J. “Sea-Level Rise from the Late 19th to the Early 21st Century.” Surv Geophys 32, 585–602 (2011). https://link.springer.com/article/10.1007/s10712-011-9119-1
2 Note that these estimates vary depending on the source. However, the general trend of an increasing rate of increase is consistent across sources.
3 EPA. “Climate Change Indicators: Sea Level.” https://www.epa.gov/climate-indicators/climate-change-indicators-sea-level#ref1
4 Lindsey, R. “Climate Change: Global Sea Level.” Climate.gov. https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level
Bennett Sherry
Bennett Sherry holds a PhD in history from the University of Pittsburgh and has undergraduate teaching experience in world history, human rights, and the Middle East at the University of Pittsburgh and the University of Maine at Augusta. Additionally, he is a research associate at Pitt’s World History Center. Bennett writes about refugees and international organizations in the twentieth century.
Credit: “Data Introduction: Direct Impacts of Climate Change ”, Bennett Sherry / OER Project, https://www.oerproject.com/
Image credits
This work is licensed under CC BY 4.0 except for the following:
Cover image: Direct effects of climate change: drought, crop stress, and sea level rise. © piyaset / iStock / Getty Images Plus.
Effect of sea level rise on homes in Summer Haven, Florida. © Aerial_Views / E+ / Getty Images.
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