Summer 2023 has been the hottest on record by a huge margin. Hundreds of millions of people suffered as heat waves cooked Europe, Japan, Texas and the Southwestern U.S. Phoenix hit 110 degrees Fahrenheit (43 degrees Celsius) for a record 54 days, including a 31-day streak in July. Large parts of Canada were on fire. Lahaina, Hawaii, burned to the ground.

As an atmospheric scientist, I get asked at least once a week if the wild weather we’ve been having is “caused” by climate change. This question reflects a misunderstanding of the difference between weather and climate.

Consider this analogy from the world of sports: Suppose a baseball player is having a great season, and his batting average is twice what it was last year. If he hits a ball out of the park on Tuesday, we don’t ask whether he got that hit because his batting average has risen. His average has gone up because of the hits, not the other way around. Perhaps the Tuesday homer resulted from a fat pitch, or the wind breaking just right, or because he was well rested that day. But if his batting average has doubled since last season, we might reasonably ask if he’s on steroids.

Unprecedented heat and downpours and drought and wildfires aren’t “caused by climate change” – they are climate change.

The rise in frequency and intensity of extreme events is by definition a change in the climate, just as an increase in the frequency of base hits causes a better’s average to rise.

And as in the baseball analogy, we should ask tough questions about the underlying cause. While El Niño is a contributor to the extreme heat this year, that warm event has only just begun. The steroids fueling extreme weather are the heat-trapping gases from burning coal, oil and gas for energy around the world.

Nothing ‘normal’ about it

A lot of commentary uses the framing of a “new normal,” as if our climate has undergone a step change to a new state. This is deeply misleading and downplays the danger. The unspoken implication of “new normal” is that the change is past and we can adjust to it as we did to the “old normal.”

Unfortunately, warming won’t stop this year or next. The changes will get worse until we stop putting more carbon dioxide and other greenhouse gases into the atmosphere than the planet can remove.

The excess carbon dioxide humans have put into the atmosphere raises the temperature – permanently, as far as human history is concerned. Carbon dioxide lingers in the atmosphere for a long time, so long that the carbon dioxide from a gallon of gasoline I burn today will still be warming the climate in thousands of years.

That warming increases evaporation from the planet’s surface, putting more moisture into the atmosphere to fall as rain and snow. Locally intense rainfall has more water vapor to work with in a warmer world, so big storms drop more rain, causing dangerous floods and mudslides like the ones we saw in Vermont, California, India and other places around the world this year.

By the same token, anybody who’s ever watered the lawn or a garden knows that in hot weather, plants and soils need more water. A hotter world also has more droughts and drying that can lead to wildfires.

So, what can we do about it?

Not every kind of bad weather is associated with burning carbon. There’s scant evidence that hailstorms or tornadoes or blizzards are on the increase, for example. But if summer 2023 shows us anything, it’s that the extremes that are caused by fossil fuels are uncomfortable at best and often dangerous.

Without drastic emission cuts, the direct cost of flooding has been projected to rise to more than US$14 trillion per year by the end of the century and sea-level rise to produce billions of refugees. By one estimate, unmitigated climate change could reduce per capita income by nearly a quarter by the end of the century globally and even more in the Global South if future adaptation is similar to what it’s been in the past. The potential social and political consequences of economic collapse on such a scale are incalculable.

Fortunately, it’s quite clear how to stop making the problem worse: Re-engineer the world economy so that it no longer runs on carbon combustion. This is a big ask, for sure, but there are affordable alternatives.

Clean energy is already cheaper than old-fashioned combustion in most of the world. Solar and wind power are now about half the price of coal- and gas-fired power. New methods for transmitting and storing power and balancing supply and demand to eliminate the need for fossil fuel electricity generation are coming online around the world.

In 2022, taxpayers spent about $7 trillion subsidizing oil and gas purchases and paying for damage they caused. All that money can go to better uses. For example, the International Energy Agency has estimated the world would need to spend about $4 trillion a year by 2030 on clean energy to cut global emissions to net zero by midcentury, considered necessary to keep global warming in check.

Just as the summer of 2023 was among the hottest in thousands of years, 2024 will likely be hotter still. El Niño is strengthening, and this weather phenomenon has a history of heating up the planet. We will probably look back at recent years as among the coolest of the 21st century.

Scott Denning has received research funding from the US National Science Foundation, the US National Aeronautical and Space Administration, the US Department of Energy, and the National Oceanic and Atmospheric Administration. He serves non the Board of Trustees for the GEOS Institute, a nonprofit company that advises communities on adaptation to our changing climate.

Summer 2023 has been the hottest on record by a huge margin. Hundreds of millions of people suffered as heat waves cooked Europe, Japan, Texas and the Southwestern U.S. Phoenix hit 110 degrees Fahrenheit (43 degrees Celsius) for a record 54 days, including a 31-day streak in July. Large parts of Canada were on fire. Lahaina, Hawaii, burned to the ground.

As an atmospheric scientist, I get asked at least once a week if the wild weather we’ve been having is “caused” by climate change. This question reflects a misunderstanding of the difference between weather and climate.

Consider this analogy from the world of sports: Suppose a baseball player is having a great season, and his batting average is twice what it was last year. If he hits a ball out of the park on Tuesday, we don’t ask whether he got that hit because his batting average has risen. His average has gone up because of the hits, not the other way around. Perhaps the Tuesday homer resulted from a fat pitch, or the wind breaking just right, or because he was well rested that day. But if his batting average has doubled since last season, we might reasonably ask if he’s on steroids.

Unprecedented heat and downpours and drought and wildfires aren’t “caused by climate change” – they are climate change.

The rise in frequency and intensity of extreme events is by definition a change in the climate, just as an increase in the frequency of base hits causes a better’s average to rise.

And as in the baseball analogy, we should ask tough questions about the underlying cause. While El Niño is a contributor to the extreme heat this year, that warm event has only just begun. The steroids fueling extreme weather are the heat-trapping gases from burning coal, oil and gas for energy around the world.

Nothing ‘normal’ about it

A lot of commentary uses the framing of a “new normal,” as if our climate has undergone a step change to a new state. This is deeply misleading and downplays the danger. The unspoken implication of “new normal” is that the change is past and we can adjust to it as we did to the “old normal.”

Unfortunately, warming won’t stop this year or next. The changes will get worse until we stop putting more carbon dioxide and other greenhouse gases into the atmosphere than the planet can remove.

The excess carbon dioxide humans have put into the atmosphere raises the temperature – permanently, as far as human history is concerned. Carbon dioxide lingers in the atmosphere for a long time, so long that the carbon dioxide from a gallon of gasoline I burn today will still be warming the climate in thousands of years.

That warming increases evaporation from the planet’s surface, putting more moisture into the atmosphere to fall as rain and snow. Locally intense rainfall has more water vapor to work with in a warmer world, so big storms drop more rain, causing dangerous floods and mudslides like the ones we saw in Vermont, California, India and other places around the world this year.

By the same token, anybody who’s ever watered the lawn or a garden knows that in hot weather, plants and soils need more water. A hotter world also has more droughts and drying that can lead to wildfires.

So, what can we do about it?

Not every kind of bad weather is associated with burning carbon. There’s scant evidence that hailstorms or tornadoes or blizzards are on the increase, for example. But if summer 2023 shows us anything, it’s that the extremes that are caused by fossil fuels are uncomfortable at best and often dangerous.

Without drastic emission cuts, the direct cost of flooding has been projected to rise to more than US$14 trillion per year by the end of the century and sea-level rise to produce billions of refugees. By one estimate, unmitigated climate change could reduce per capita income by nearly a quarter by the end of the century globally and even more in the Global South if future adaptation is similar to what it’s been in the past. The potential social and political consequences of economic collapse on such a scale are incalculable.

Fortunately, it’s quite clear how to stop making the problem worse: Re-engineer the world economy so that it no longer runs on carbon combustion. This is a big ask, for sure, but there are affordable alternatives.

Clean energy is already cheaper than old-fashioned combustion in most of the world. Solar and wind power are now about half the price of coal- and gas-fired power. New methods for transmitting and storing power and balancing supply and demand to eliminate the need for fossil fuel electricity generation are coming online around the world.

In 2022, taxpayers spent about $7 trillion subsidizing oil and gas purchases and paying for damage they caused. All that money can go to better uses. For example, the International Energy Agency has estimated the world would need to spend about $4 trillion a year by 2030 on clean energy to cut global emissions to net zero by midcentury, considered necessary to keep global warming in check.

Just as the summer of 2023 was among the hottest in thousands of years, 2024 will likely be hotter still. El Niño is strengthening, and this weather phenomenon has a history of heating up the planet. We will probably look back at recent years as among the coolest of the 21st century.

Scott Denning has received research funding from the US National Science Foundation, the US National Aeronautical and Space Administration, the US Department of Energy, and the National Oceanic and Atmospheric Administration. He serves non the Board of Trustees for the GEOS Institute, a nonprofit company that advises communities on adaptation to our changing climate.

Earthquakes, large and small, happen every single day along zones that wrap around the world like seams on a baseball. Most don’t bother anybody, so they don’t make the news. But every now and then a catastrophic earthquake hits people somewhere in the world with horrific destruction and immense suffering.

On Sept. 8, 2023, a magnitude 6.8 earthquake in the Atlas Mountains of Morocco shook ancient villages apart, leaving thousands of people dead in the rubble. In February 2023, a large area of Turkey and Syria was devastated by two major earthquakes that hit in close succession.

As a geologist, I study the forces that cause earthquakes. Here’s why some seismic zones are very active while others may be quiet for generations before the stress builds into a catastrophic event.

Earth’s crust crashes into itself and pulls apart

Earthquakes are part of the normal behavior of the Earth. They occur with the movement of the tectonic plates that form the outer layer of the planet.

You can think of the plates as a more or less rigid outer shell that has to shift to allow the Earth to give off its internal heat.

These plates carry the continents and the oceans, and they are continuously in slow-motion crashes with one another. The cold and dense oceanic plates dive under continental plates and back into Earth’s mantle in a process known as subduction. As an oceanic plate sinks, it drags everything behind it and opens a rift somewhere else that is filled by rising hot material from the mantle that then cools. These rifts are long chains of underwater volcanoes, known as mid-ocean ridges.

Earthquakes accompany both subduction and rifting. In fact, that is how the plate boundaries were first discovered.

In the 1950s, when a global seismic network was established to monitor nuclear tests, geophysicists noticed that most earthquakes occur along relatively narrow bands that either fringe the edges of ocean basins, as in the Pacific, or cut right down the middle of basins, as in the Atlantic.

They also noticed that earthquakes along subduction zones are shallow on the oceanic side but get deeper under the continent. If you plot the earthquakes in 3D, they define slablike features that trace the plates sinking into the mantle.

An experiment: How an earthquake works

To understand what happens during an earthquake, put the palms of your hands together and press with some force. You are modeling a plate boundary fault. Each hand is one plate, and the surface of your hands is the fault. Your muscles are the plate tectonic system.

Now, add some forward force to your right hand. You will find that it will eventually jerk forward when the forward force overcomes the friction between your palms. That sudden forward jerk is the earthquake.

Scientists explain earthquakes using what’s known as the elastic rebound theory.

Fast plates move at up to 8 inches (20 centimeters) per year, driven mostly by the oceanic slabs sinking at subduction zones. Over time, they become stuck to each other by friction at the plate boundary. The attempted motion deforms the plate boundary zone elastically, like a loaded spring. At some point, the accumulated elastic energy overcomes the friction and the plate jerks forward, causing an earthquake.

But the plate-driving forces do not stop, so the plate boundary starts to accumulate elastic energy again, which will cause another earthquake – perhaps soon or perhaps far in the future.

In the oceans, plate boundaries are narrow and well defined because the underlying rocks are very stiff. But within the continents, plate boundaries are often broad zones of deformed mountainous terrain crisscrossed by many faults. Those faults may persist for eons, even if the plate boundary becomes inactive. That is why sometimes earthquakes occur far from plate boundaries.

Earthquakes, fast and slow

The cyclic behavior of faults allows seismologists to estimate earthquake risks statistically. Plate boundaries with fast motions, such as the ones along the Pacific rim, accumulate elastic energy rapidly and have the potential for frequent large-magnitude earthquakes.

Slow-moving plate boundary faults take longer to reach a critical state. Along some faults, hundreds or even thousands of years can pass between large earthquakes. This allows time for towns to grow and for people to lose ancestral memory of past earthquakes.

The earthquake in Morocco is an example. Morocco is located on the boundary between the African and the Eurasian plates, which are slowly crashing into each other.

The huge belt of mountains that extends from the Atlas of North Africa to the Pyrenees, Alps and most of the mountains across southern Europe and the Middle East is the product of this plate collision. Yet because these plate motions are slow near Morocco, large earthquakes are not so frequent.

Preparing for the big one

An important fact about catastrophic earthquakes is that, in most cases, the earthquakes don’t kill people – falling buildings do.

Most Americans have heard of California’s San Andreas Fault and the seismic risk to San Francisco and Los Angeles. The last major earthquake along the San Andreas Fault hit at Loma Prieta, in the San Francisco Bay area, in 1989. Its magnitude, 6.9, was comparable to that of the earthquake in Morocco, yet 63 people died compared with thousands. That’s largely because building codes in these earthquake-prone U.S. cities are now designed to keep structures standing when the Earth shakes.

The exceptions are tsunamis, the huge waves generated when an earthquake shifts the seafloor, displacing the water above it. A tsunami that hit Japan in 2011 had horrific consequences, regardless of the quality of engineering in coastal towns.

Unfortunately, earthquake scientists can’t predict exactly when an earthquake might occur; they can only estimate the hazard.

Jaime Toro has received funding from NSF, USGS and DOE in the past.