Climate Crisis and Ocean Warming


The earth is an ocean planet. Covering 70% of the globe, the ocean absorbs about 90% of the atmosphere’s heat. The world’s oceans interact with the global climate and weather: oceans influence the climate and weather locally and globally; and the climate can change the oceans.

Using Climate Stripes you can see how much your region has warmed between 1906 and 2018.

This graph shows the amount of carbon dioxide in the atmosphere as of December 22, 2018.

As the atmosphere has warmed due to human-driven climate change, the ocean has taken up an inordinate amount of heat. And, that has taken a toll: the ocean is warmer than at any time since we began keeping records in the 1880s. In January 2018 scientists reported that the ocean is warming 40% faster than had been predicted five years earlier.

The warming of the ocean has many dire consequences: sea level rise, coral bleaching, decrease in oxygen levels, algal blooms, species moving or dying if they can’t adapt, and changing currents.

In addition, the ocean also absorbs 25% of the atmosphere’s carbon dioxide. As the carbon dioxide in the atmosphere increases and the ocean absorbs it, the ocean’s chemistry changes, becoming more acidic. This ocean acidification has impacts on sea creatures. Scientists have been investigating the potential effects over the last 25 years. Many shell-building animals are already showing signs of this stress.

Ocean Warming

We call it a climate crisis now; earlier in our understanding we called what the earth is experiencing “global warming.” It could also be called “ocean warming” since the oceans have absorbed more than 90% of that warming, as this graph shows.

The oceans are holding more and more heat; they are  heating up faster than scientists had predicted.

Scientists have been tracking ocean warming around the globe. Where, how much, how quickly did the ocean warm, and how much heat will it absorb in the future, “are questions that send satellites orbiting around the globe and take oceanographers to the far reaches of the sea. Measuring the magnitude and rate of ocean heat uptake is a very complex and challenging task that requires enormous observational and modeling effort.”

Sea Level Rise

Seas are rising around the globe because the earth is warming. There are two contributing factors to the rise: sea water expands as it warms; and ice sheets and glaciers are melting into the ocean. For the past 25 years the seas have not only been rising and the rate of that rise is increasing. By 2100, the seas could rise anywhere between five inches and 10 feet, depending on what actions we take.

Satellites can measure sea level rise from space. And you can see a visualization of sea level rise measurements over a 22-year period.

If you live on the coast, you can find a place near you to see how much the sea will rise and the risks associated with it. If you’re not near the coast, you can find a place of interest anywhere in the world.

A new report shows that seas are rising faster than scientists had predicted. Within three decades rising sea levels could push chronic floods higher than land currently home to 300 million people. Indeed, scientists found an accelerating rate of sea-level rise in 2019 at nearly all tidal stations along the U.S. coastline. “Rates of sea-level rise accelerated at all 21 of the report-card stations along the U.S. East and Gulf coasts, and at 7 of the 8 monitored stations along the U.S. West coast, excluding Alaska.”

Forests are already dying because of rising seas

Coral Bleaching

Extensive coral bleaching in the Kimberley region, Western Australia, April 2016 Credit, Morane Le Nohaic

Coral bleaching is caused by higher ocean temperatures, which starve the coral reefs of their main food source, microscopic algae. When the ocean is too warm for the symbiotic algae that live in coral tissues, they leave the corals or die – a process called bleaching. The frequency of coral bleaching is increasing. In the past, coral reefs bleached every 25 to 30 years. Since 2010, that timeframe has shrunk to six years. By early 2018, the Great Barrier Reef alone has bleached four times since 1998.

Some coral reefs can recover if there’s enough time between bleaching events. But if corals can’t adapt quickly enough, “we could be looking at the effective loss of most of the world’s coral reefs,” said Mark Eakin, an oceanographer who is coordinator of the Coral Reef Watch project at the United States National Oceanographic and Atmospheric Administration that looks at loss of world's coral reefs.

You can see images of healthy and unhealthy reefs here

The climate crisis is affecting coral reefs in a couple of ways.

The Great Barrier reef, the largest coral reef in the world, is in danger because of climate change

People can help coral reefs to recover more quickly from coral bleaching by reducing local stressors.

Some coral reefs recover more quickly than others, for example those around Palmyra Island.

Scientists are experimenting with helping corals to recover that have the best natural chances of survival. And in some places people are coral farming — a process whereby fragments of corals are collected from the local reefs, raised in nurseries on land until mature, and then installed at a site targeted for  restoration.

Some corals seem to be preparing for an extinction crisis with “disaster traits” that resemble those from last major extinction crisis 65 million years ago; for example: “increased prevalence of deep-water residing, cosmopolitan distributions, non-symbiotic relationship to algae, solitary or small colonies, and bleaching resistance.”

Oxygen Decreasing

Graphic courtesy of Matthew Long, NCAR.

The decline in oxygen is already happening in some places and will get worse over the coming decades. A scientific report in December 2019 found that oxygen levels in the world’s oceans declined by roughly 2 percent between 1960 and 2010.

As oceans heat up, they hold less oxygen than cooler water. In the open ocean, global warming is the main cause of declining oxygen. Direct measurements show the amount of oxygen in the global oceans has decreased by around 2% over the past 50 years. Oxygen is fundamental to biological processes in the ocean. Its decline can cause changes in biodiversity, productivity and nutrient cycling.

Harmful Algal Blooms

Scientists have shown that rising ocean temperatures caused by human-induced climate change have already driven an intensification of harmful algal blooms (HABs). Harmful algal blooms (HAB) have been in the news for several years now. They occur when nutrient pollution from land reaches the sea or freshwater, fueling runaway growth of algae that can use up all the oxygen. Algal blooms are most often the result of run-off from fertilizer applied to farmlands, or livestock or human wastewater runoff. The blooms can produce toxins that when large enough can kill marine life from tiny to very big.


In the fall of 2018, a red tide of a toxic algal bloom covered much of the west coast of Florida. The algae (Karenia brevis) produce a neurotoxin known to kill fish and other animals. Florida resource managers estimate that about 267 tons of fish, manatees, whale sharks, and dolphins were killed by this bloom. Such intense blooms can cause problems for human health and tourism as well.

On the west coast, Dungeness crab fishermen have suffered economic losses because toxic algae blooms have made the crabs unsafe for human consumption. The crab fishermen are blaming a warming ocean caused by climate change for the algae bloom and the closure of the fishery. They are suing fossil fuel companies for damages on behalf of crab fishers, their businesses and families, and local communities in California and Oregon.

Species on the Move and Diseases

Fish in waters that have warmed are moving toward higher latitudes to stay in their preferred temperature.

But, the ocean doesn't warm uniformly, so local conditions drive fish as well. In some places, there may be pockets of cooler water south, so fish move there. For example, in the Gulf of Maine, some species are moving southwest and closer to shore to find cooler waters.

This report has good graphics about species on the move.

A warmer ocean isn’t a problem for all species. As the oceanic food web shifts, cephalopods are adapting and thriving, becoming the dominant species in many places.

Sea star wasting disease has decimated more than 20 species of sea stars on the west coast, including the iconic sun star. Although many factors seem to contribute to the disease, scientists found that the times and locations of the biggest sea star death tolls coincided with the presence of abnormally warm water.

Species moving

Species are moving all around the globe due to warming waters. Some marine animals are on the move to places with cooler temperatures. Here are some examples.

Lobsters may be finding the Gulf of Maine too warm, not good news for lobster fishing. Here’s our blog about that.

Jumbo squid are also finding waters too warm for them, contributing to the collapse of the squid fishery in the Gulf of California.

A warming ocean means plankton moving north, not a good sign for ecosystems. With so many species on the move, marine communities are reshaping.

A showy pink sea slug may be a canary in tidepools of climate change

Warming waters are causing fish in Icelandic waters to move north “Ocean temperatures around Iceland have increased between 1.8 and 3.6 degrees Fahrenheit over the past 20 years.” Fishing communities are struggling as the fish, especially capelin, have moved to cooler waters.


Disease outbreaks, most likely made worse by warming waters, have hit a variety of species.


The changes in the ocean are killing some species.

Some species that can’t move any more are trapped with no place to go or are facing local extinctions. The research found that of the marine species they studied, 56 percent experienced a range contraction due to global warming, compared to 27 percent of the land species.

For species that can’t move, marine heat waves can be deadly.

And for animals that migrate, like gray whales, food may be scarce causing malnutrition and death.

Currents and Upwelling

“The global ocean conveyor belt is a constantly moving system of deep-ocean circulation driven by temperature and salinity. The great ocean conveyor moves water around the globe. ... Cold, salty water is dense and sinks to the bottom of the ocean while warm water is less dense and remains on the surface.” NOAA

Scientists are making the connection between climate change and changes in ocean circulation. The global system of deep-ocean circulation is driven by temperature and salinity. Scientists think that ocean circulation is slowing in the Atlantic ocean because of climate change: evidence shows it has slowed by about 15 percent since the middle of the last century. But recently scientists looking at the entire globe have found that currents have been speeding up for the last 25 years due to the warming of the planet.

Cold freshwater from melting Greenland ice is probably the main cause. This water disrupts the ocean conveyor belt at a delicate point, where the cooled surface water starts sinking. Ocean circulation is a major factor driving weather patterns. Slower circulation in the Atlantic means higher hurricane risks, hotter summers in Europe and changing rainfall in the tropics.

Warming oceans alter the patterns of ocean circulation in other ways: warmer surface layers slow the mixing of nutrients from deep water so there is less fertilizer for marine algae near the surface. The microscopic marine algae provide oxygen for the Earth’s atmosphere and form the basis for ocean food webs.


Weather or climate? Differentiating the two can be confusing. Climate is the long term average of the weather over the years. This is a  great explanation by Neil De Grasse Tyson.

Today the weather may be warm and dry where you live; tomorrow it might rain- that’s weather. Thinking of the U.S. as a whole, we know the south generally has warmer weather than in the northeast and Alaska-- that’s climate.


Long-Term Perspective Matters Most

It’s the long-term average of the entire planet that really matters when we talk about the changes in the weather due to climate change. Today the planet is “running a fever” as Dr. Katherine Hayhoe explains. Over the second half of the 20th and the first decades of the 21st centuries the climate has warmed. The map below shows Earth’s average global temperature from 2013 to 2017 as compared to a baseline global average temperature from 1951 to 1980. Yellows, oranges and reds show regions with a warmer climate than the earlier baseline.

Credit: NASA’s Scientific Visualization Studio.


The warming of the earth’s climate means more intense weather. In a study released in March 2020, Stanford researchers found that climate change is intensifying heat waves and heavy rainfall events faster than scientists had predicted. One explanation for this: the Arctic is warming faster than the rest of the planet, which affects the weather patterns in the northern hemisphere, causing persistent weather extremes like heat waves, drought, floods, and wildfires.


The decade 2010-2019 saw so much damage from extreme weather events in the U.S. that 258 of them reached one billion dollars in costs. And, in every year between 2015-2019, ten or more separate billion-dollar disaster events impacted the U.S.  

As the map below shows, some parts of the world will have a wetter climate, some a drier one by the end of the century if emissions aren’t reduced.

Projected change in annual average precipitation by the end of the 21st century, based on a medium emissions scenario (SRES A1B) (NOAA GFDL, 2008).


If you want to see where extreme weather events that can be attributed to climate change occurred around the globe, this interactive map shows you. Those events include: extreme heat, drought, more intense storms, and wildfires.

There were big devasting wildfires in Australia in December-February 2019/2020, but the country has seen a long-term increase in the risk of fires and a lengthening bushfire season due to climate change. Drought and more extreme heat waves have created ideal conditions for bushfires. Climate modelers confirmed that, “Climate change played a major role, making the hazardous conditions that led to Australia’s monstrous blazes at least 30 percent more likely than they would have been without human-caused global warming.” Read our blog about the fires.

The Camp Fire as seen from Landsat satellite. By NASA, Joshua Stevens -


Devastating wildfires are occurring in other places: in California, where we live, wildfires have increased in frequency and severity. California’s wildfire activity has increased for five decades with five of the state’s largest fires occurring since 2006. A Columbia University study found that climate change is the leading driver of that increase.

It’s not only wildfires that have caused more destruction, it’s also hurricanes. Climate change is making hurricanes more dangerous with increased rain and storm surge height, and increased wind speeds. A new study found that Hurricane Florence (2018) delivered more precipitation and was spatially larger definitely due to climate change. The increase in precipitation hurricanes deliver is due to the combination of warmer air over warmer ocean water where the hurricanes form and grow. In 2017 Hurricane Harvey dumped a “biblical” 60 inches of rain on southeast Texas. Also in 2017, Hurricane Maria delivered more rain on average than any of the 129 storms that struck the Puerto Rico in the last 60 years. Research found that this increase was “due largely to the effects of human-induced warming.”

Hurricane Harvey from the Terra satellite.

Ocean Acidification

The increasing amount of carbon dioxide dissolved in oceans is leading to more acidic seawater that is harmful to many kinds of marine life. Sometimes called climate change’s “evil twin,” ocean acidification poses a critical threat to shell building organisms: they make thinner shells and the shells of some species are actually dissolving.

Pteropod: inset is dissolving shell

Some animals that use calcium carbonate to build shells and skeletons face challenges. Pteropods, free-swimming sea snails called sea butterflies, are often the primary zooplankton at the base the food web in arctic and subarctic waters. These animals may be unable to maintain shells in waters with less available calcium carbonate. Scientists are already seeing pteropods with damaged shells.

This is also true for coral reefs, which are made of calcium carbonate skeletons. To make their skeletons, corals need two ingredients: calcium ions and carbonate ions. Acids react with carbonate ions, in effect making them unavailable.

As the ocean absorbs more carbon dioxide, carbonate ions become scarcer. Corals have to expend more energy to collect them, reducing their ability to build their skeletons. Stanford University scientists have produced a 360-degree virtual underwater ecosystem “to provide an up-close look at how coral reefs might appear by the end of the century if emissions aren’t curbed.”

Marine arthropods also make their shells from calcium carbonate. Crabs, for example, are vulnerable to the changes in ocean chemistry. This toolkit contains information and images about how ocean acidification is impacting Dungeness crab.

This changing ocean chemistry will reverberate through every coastal and marine ecosystem. Read our blog about how and why the waters of the west coast are acidifying more quickly than the global ocean.

Scientists have found that ocean acidification is affecting the way sound is transmitted, which impacts the marine mammals that depend on sound for communication and finding food.

Ocean acidification is affecting shellfish in our diet. Oysters, mussels, scallops, and other shellfish need calcium carbonate to build their shells. With increasing acidity, the shells are thinner, growth is slower and death rates rise. Oyster farmers in the Pacific Northwest are already seeing problems with shell growth in young oysters.

The ocean’s increasing acidification will change the way we eat. The good news is that scientists think that natural genetic variations may help some animals adapt to a more acidic ocean. 

Since the industrial revolution, ocean acidity has increased about 30% and it is expected to increase by 100-150% by 2100 if CO2 emissions continue in a business-as-usual scenario.


Scientists working in the Monterey Bay are conducting field studies to see the impact of ocean acidification locally.

Test your knowledge of ocean acidification in this interactive

Protection and Resilience

The ocean can become central to slowing climate change since we know it has absorbed most of the earth’s excess heat. But we need to keep it healthy and, in some places, restore ocean ecosystems. If  we stop overfishing, polluting and destroying habitats that undermine the ocean’s ability to bounce back from the impacts of climate change already underway, oceans and coasts will help mitigate the climate crisis. Biodiversity in marine habitats creates resilience.

Wetlands, coral and oyster reefs, and seagrass and kelp beds help shield our coasts from the full force of intensifying storms and sea level rise. Kelp and seagrass beds dampen wave force and sequester carbon. Wetlands buffer coastlines from sea level rise and storm surge, making communities more resilient. They also sequester carbon. Coral reefs protect coasts from storm waves and surge. Oyster reefs also can protect coasts from the impacts of climate change in the same way. Restoring and protecting these habitats is critical to coastal resilience.

We know that Marine Protected Areas (MPAs) are a good tool for building ocean resilience to climate change. MPAs are geographically defined areas of the ocean where natural resources are given greater protection than the surrounding waters. According to NOAA, MPAs are a key tool for maintaining and restoring ecosystem resilience in a changing climate.”

There are many ideas for how the ocean can provide some solutions to climate change. All the solutions presented here are not equal and some are probably dangerous.

Teaching about the Climate Crisis

A new NPR/Ipsos poll shows that 80% of parents wish that schools taught climate change.

And even more teachers— 86%— agreed that climate change should be taught in schools. NSTA recently issued a position statement “calling for greater support for science educators in teaching evidence-based science, including climate science and climate change.

There are many challenges to teaching about the climate crisis. The topic is, in some places is political and highly charged.

Teachers need to look carefully at the sources of climate change education materials. “The school systems of the country are so fragmented and under-resourced that they have no choice but to turn to people like the oil industry who offer them free stuff,” Charles Anderson, a professor of science education at Michigan State University, told the Associated Press last year.

Now students are demanding climate change education. 2019 was considered the year of the “climate strike,” with student-led massive climate demonstrations. One of the heroines behind the popularity of climate strikes is 16-year-old Greta Thunberg. Looking at signs from these events, it’s clear that many students have “climate anxiety” and distress. “Seven in 10 teenagers and young adults in the United States say climate change will cause harm to their generation.” Here are some guidelines for talking with children about climate change.

Teaching Resources:

The Climate Literacy and Energy Awareness Network (CLEAN) is a great resource for materials for teaching about the climate crisis. We’ve looked at some of the lessons and resources and recommend the ones below:

The National Council for Science Education (NCSE) mission is “We give science teachers the tools and skills they need to help their students overcome misconceptions and misinformation about climate change and evolution.”

They have many climate change resources, Teaching Ambassadors, and lessons including those below.

NPR gives ideas for teaching climate change in the classroom. If graphs can help, here are some.

Green Ninja has many resources about climate change for upper elementary and middle school students.

NASA has resources for explaining climate science with games, activities and videos.

Some students have created their own  podcasts about climate change.

Edutopoia has examples and resources about teaching the climate crisis across disciplines, as does the Climate Generation.

Teaching Climate Crisis Solutions:

This sophisticated interactive lets high school students, and above, understand the possible solutions to the climate crisis by simulating solutions.

NOAA has a lesson plan about responding to climate change.