Less than a month into summer 2024, the vast majority of the U.S. population has already experienced an extreme heat wave. Millions of people were under heat warnings across the western U.S. in early July or sweating through humid heat in the East.

Death Valley hit a dangerous 129 degrees Fahrenheit (53.9 C) on July 7, a day after a motorcyclist died from heat exposure there. Las Vegas broke its all-time heat record at 120 F (48.9 C). In California, days of over-100-degree heat in large parts of the state dried out the landscape, fueling wildfires. Oregon reported several suspected heat deaths.

Extreme heat like this has been hitting countries across the planet in 2024.

Globally, each of the past 13 months has been the hottest on record for that month, including the hottest June, according to the European Union’s Copernicus climate service. The service reported on July 8, 2024, that the average temperature for the previous 12 months had also been at least 1.5 C (2.7 F) warmer than the 1850-1900 pre-industrial average.

The 1.5 C warming threshold can be confusing, so let’s take a closer look at what that means. In the Paris climate agreement, countries worldwide agreed to work to keep global warming under 1.5 C, however that refers to the temperature change averaged over a 30-year period. A 30-year average is used to limit the influence of natural year-to-year fluctuations.

So far, the Earth has only crossed that threshold for a single year. However, it is still extremely concerning, and the world appears to be on track to cross the 30-year average threshold of 1.5 C within 10 years.

We study weather patterns involving heat. The early season heat, part of a warming trend fueled by humans, is putting lives at risk around the world.

Heat is becoming a global problem

Record heat has hit several countries across the Americas, Africa, Europe and Asia in 2024. In Mexico and Central America, weeks of persistent heat starting in spring 2024 combined with prolonged drought led to severe water shortages and dozens of deaths.

Extreme heat turned into tragedy in Saudi Arabia, as over 1,000 people on the Hajj, a Muslim pilgrimage to Mecca, collapsed and died. Temperatures reached 125 F (51.8 C) at the Grand Mosque in Mecca on June 17.

Hospitals in Karachi, Pakistan, were overwhelmed amid weeks of high heat, frequent power outages, and water shortages in some areas. Neighboring India faced temperatures around 120 F (48.9 C) for several days in April and May that affected millions of people, many of them without air conditioning.

In Greece, where temperatures were over 100 F (37.8 C) for days in June, several tourists died or were feared dead after going hiking in dangerous heat and humidity.

Japan issued heatstroke alerts in Tokyo and more than half of its prefectures as temperatures rose to record highs in early July.

The climate connection: This isn’t ‘just summer’

Although heat waves are a natural part of the climate, the severity and extent of the heat waves so far in 2024 are not “just summer.”

A scientific assessment of the fierce heat wave in the eastern U.S. in June 2024 estimates that heat so severe and long-lasting was two to four times more likely to occur today because of human-caused climate change than it would have been without it. This conclusion is consistent with the rapid increase over the past several decades in the number of U.S. heat waves and their occurrence outside the peak of summer.

These record heat waves are happening in a climate that’s globally more than 2.2 F (1.2 C) warmer – when looking at the 30-year average – than it was before the industrial revolution, when humans began releasing large amounts of greenhouse gas emissions that warm the climate.

While a temperature difference of a degree or two when you walk into a different room might not even be noticeable, even fractions of a degree make a large difference in the global climate.

At the peak of the last ice age, some 20,000 years ago, when the Northeast U.S. was under thousands of feet of ice, the globally averaged temperature was only about 11 F (6 C) cooler than now. So, it is not surprising that 2.2 F (1.2 C) of warming so far is already rapidly changing the climate.

If you thought this was hot

While this summer is likely be one of the hottest on record, it is important to realize that it may also be one of the coldest summers of the future.

For populations that are especially vulnerable to heat, including young children, older adults and outdoor workers, the risks are even higher. People in lower-income neighborhoods where air conditioning may be unaffordable and renters who often don’t have the same protections for cooling as heating will face increasingly dangerous conditions.

Extreme heat can also affect economies. It can buckle railroad tracks and cause wires to sag, leading to transit delays and disruptions. It can also overload electric systems with high demand and lead to blackouts just when people have the greatest need for cooling.

The good news: There are solutions

Yes, the future in a warming world is daunting. However, while countries aren’t on pace to meet their Paris Agreement goals, they have made progress.

In the U.S., the 2022 Inflation Reduction Act has the potential to reduce U.S. greenhouse gas emissions by nearly half by 2035.

Switching from air conditioners to heat pumps and network geothermal systems can not only reduce fossil fuel emissions but also provide cooling at a lower cost. The cost of renewable energy continues to plummet, and many countries are increasing policy support and incentives.

There is much that humanity can do to limit future warming if countries, companies and people everywhere act with urgency. Rapidly reducing fossil fuel emissions can help avoid a warmer future with even worse heat waves and droughts, while also providing other benefits, including improving public health, creating jobs and reducing risks to ecosystems.

This is an update to an article originally published on June 26, 2024.

Mathew Barlow, Professor of Climate Science, UMass Lowell and Jeffrey Basara, Professor of Meteorology, UMass Lowell

This article is republished from The Conversation under a Creative Commons license. Read the original article.

When wildfires rage, the immediate threat is obvious – but smoke from the fires actually kills far more people than the flames.

As fires become more frequent, that smoke is leading to a public health crisis.

In a new study published in the journal Science Advances, we found that wildfire smoke likely contributed to more than 52,000 premature deaths across California alone from 2008 to 2018, with an economic impact from the deaths of more than US$430 billion.

Previous studies have examined the short-term health risks from wildfire smoke, but few have assessed how exposure to wildfire smoke over years adds up to shorten human lives.

Wildfire risk and severity have grown as the climate has changed and as more people have moved into the edges of wildland areas, increasing the risk that they will start fires. Years of putting out all wildfires have also kept small fires from clearing out the undergrowth, meaning the fires that do escape have more fuel to burn.

As fires are becoming a regular occurrence in all of our lives, it’s important for communities to understand that the health risk from smoke pollution is rising, too.

Health risks

Decades of air pollution research have shown how exposure to fine particulate matter, or PM_2.5, can harm a person’s long-term health.

PM_2.5 is a mixture of small particles, each only a fraction of the width of a human hair. It comes from a variety of sources, such as vehicle tailpipes and factory emissions, as well as from other sources, including fires. The particles are so tiny, they can travel deep into the lungs and even enter the bloodstream.

Inhaling PM_2.5 can cause short-term respiratory health problems in vulnerable populations, such as people with asthma and older adults. It also leads to long-term harm by contributing to the formation of chronic diseases, including atherosclerosis, asthma, decreases in lung function and diabetes. One reason this happens is the body’s inflammatory response to inhaling air pollutants.

Wildfire smoke contains a stew of chemicals. A growing body of research indicates that wildfire PM_2.5 may have unique physical and chemical components that increase toxicity. For example, a study from the University of California, Davis, showed that wildfire smoke caused more inflammation in the lungs of rats than PM_2.5 from other sources such as cars and industry. This makes the pollutant potentially more harmful to human respiratory health compared with the typical PM_2.5 that people are exposed to in urban environments.

The problem with wildfire smoke

We examined the long-term health damages from breathing wildfire smoke. The results, from over a decade, suggest that in years with lots of fire activities – 2017 and 2018, for example – wildfire smoke contributed to more than 10,000 deaths annually in California. For comparison, about 4,000 people die in California from traffic accidents each year.

Even though most fires are in rural, forested areas, smoke can travel hundreds or thousands of miles. So the health effects are widespread through population centers.

For example, California’s Rough Fire of 2015 burned more than 150,000 acres in a mostly rural area of Fresno County, but most mortality impacts in that year were west of the fire in a more populated area of the county and throughout the San Joaquin Valley. In 2018, the year the town of Paradise and several other communities burned, wildfire smoke may have killed as many as 12,000 Californians prematurely.

To conduct this analysis, we looked at annual estimates of wildfire smoke PM_2.5 by ZIP code based on wildfire activity. Unlike most past studies, we looked specifically at exposure to PM_2.5 from wildfires. This allowed us to account for that potentially increased toxicity of smoke.

Then, we used a dose-response estimate for the relationship between wildfire-specific air pollution and premature deaths. Dose-response estimates are derived from epidemiological studies that relate air pollution levels to survival. For this study, we adjusted an existing dose-response estimate to account for potential increased toxicity from wildfire smoke.

How to stay safe

These findings suggest that society needs to invest in coordinated forest management, wildland-urban interface management and climate change mitigation, all of which could yield significant public health benefits through reducing the frequency and severity of wildfires and smoke exposure. We will also need to invest more to adapt to the worsened smoke by providing safe areas in schools and other public buildings.

Here are some tips for limiting how much smoke you inhale on days when the wind is carrying wildfire smoke your way:

• Stay indoors: On heavy smoke days, don’t go outside, and close your windows. Turn on an air purifier, if you have one. If you don’t have one, considering purchasing one with a HEPA filter. The California Air Resources Board has a list of certified air filters. If you smell smoke, or know there is a fire nearby – even if you can’t see it – check a resource such as the EPA and Forest Service’s AirNow Fire and Smoke Map or the PurpleAir map to get a sense of whether it’s safe to be outdoors.

• Wear a protective mask: If you do go outside, wear a protective mask, such as an N95 if possible. If you don’t have access to an N95, a surgical mask will help too.

• Avoid exercising outdoors on smoky days: Strenuous activities such as exercise draw more air into the lungs – and with it, PM_2.5. Exercising also causes your heart and respiratory system to work harder. If you exercise, do so inside in a place with filtered air.

• Stay informed: You can follow state and federal air quality agencies in your region on their websites and social media platforms and sign up for alerts when available.

Rachel Connolly, Research Project Director, University of California, Los Angeles and Michael Jerrett, Professor of Environmental Health Sciences, University of California, Los Angeles

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Of the more than 74,000 known meteorites – rocks that fall to Earth from asteroids or planets colliding together – only 385 or so stones came from the planet Mars.

It’s not that hard for scientists to work out that these meteorites come from Mars. Various landers and rovers have been exploring Mars’ surface for decades. Some of the early missions – the Viking landers – had the equipment to measure the composition of the planet’s atmosphere. Scientists have shown that you can see this unique Martian atmospheric composition reflected in some of these meteorites.

Mars also has unique oxygen. Everything on Earth, including humans and the air we breathe, is made up of a specific composition of the three isotopes of the element oxygen: oxygen-16, oxygen-17 and oxygen-18. But Mars has an entirely different composition – it’s like a geochemical fingerprint for being Martian.

The Martian meteorites found on Earth give geologists like me hints about the makeup of the red planet and its history of volcanic activity. They allow us to study Mars without sending a spacecraft 140 million miles away.

A planet of paradoxes

These Martian meteorites formed from once red-hot magma within Mars. Once these volcanic rocks cooled and crystallized, radioactive elements within them started to decay, acting as a radiometric clock that enables scientists to tell when they formed.

From these radiometric ages, we know that some Martian meteorites are as little as 175 million years old, which is – geologically speaking – quite young. Conversely, some of the Martian meteorites are older, and formed close to the time Mars itself formed.

These Martian meteorites tell a story of a planet that has been volcanically active throughout its entire history. In fact, there’s potential for Martian volcanoes to erupt even today, though scientists have never seen such an eruption.

The rocks themselves also preserve chemical information that indicates some of the major events on Mars happened early in its history. Mars formed quite rapidly, 4.5 billion years ago, from gas and dust that made up the early solar system. Then, very soon after formation, its interior separated out into a metallic core and a solid rocky mantle and crust.

Since then, very little seems to have disturbed Mars’ interior – unlike Earth, where plate tectonics has acted to stir and homogenize its deep interior. To use a food analogy, the Earth’s interior is like a smoothie and Mars’ is like a chunky fruit salad.

Martian volcano remnants

Understanding how Mars underwent such an early and violent adolescence, yet still may remain volcanically active today, is an area of great interest to me. I would like to know what the inside of Mars looks like, and how its interior makeup might explain features, like volcanoes, on the red planet’s surface.

When geologists set out to answer questions about volcanism on Earth, we typically examine lava samples that erupted at different places or times from the same volcano. These samples allow us to disentangle local processes specific to each volcano from planetary processes that take place at a larger scale.

It turns out we can do the same thing for Mars. The rather exotically named nakhlite and chassignite meteorites are a group of rocks from Mars that erupted from the same volcanic system some 1.3 billion years ago.

Nakhlites are basaltic rocks, similar to lavas you would find in Iceland or Hawaii, with beautiful large crystals of a mineral known as clinopyroxene. Chassignites are rocks made almost entirely of the green mineral olivine – you might know the gem-quality variety of this mineral, peridot.

Along with the much more common shergottites, which are also basaltic rocks, and a few other more exotic Martian meteorite types, these categories of meteorite constitute all the rocks researchers possess from the red planet.

When studied together, nakhlites and chassignites tell researchers several things about Mars. First, as the molten rock that formed them oozed to the surface and eventually cooled and crystallized, some surrounding older rocks melted into them.

That older rock doesn’t exist in our meteorite collection, so my team had to tease out its composition from the chemical information we obtained from nakhlites. From this information, we learned that the older rock was basaltic in composition and chemically distinct from other Martian meteorites. We found that it had been chemically weathered by exposure to water and brine.

This older rock is quite different from the Martian crust samples in our meteorite collection today. In fact, it is much more like what we would expect the Martian crust to look like, based on data gathered by rover missions and satellites orbiting Mars.

We know that the magmas that made nakhlites and chassignites come from a distinct portion of Mars’ mantle. The mantle is the rocky portion between Mars’ crust and metallic core. These nakhlites and chassignites come from the solid rigid shell at the top of Mars’ mantle, known as the mantle lithosphere, and this source makes them distinct from the more common shergottites.

Shergottites come from at least two sources within Mars. They may come from parts of the mantle just beneath the lithosphere, or even the deep mantle, which is closer to the planet’s metallic core.

Understanding how volcanoes on Mars work can inform future research questions to be addressed by missions to the planet. It can also help scientists understand whether the planet has ever been habitable for life, or if it could be in the future.

Hints at habitability

Earth’s active geological processes and volcanoes are part of what makes our planet habitable. The gases emanating from volcanoes are a major part of our atmosphere. So if Mars has similar geological processes, that could be good news for the potential habitability of the red planet.

Mars is much smaller than Earth, however, and studies suggest that it’s been losing the chemical elements essential for a sustainable atmosphere since it formed. It likely won’t look anything like Earth in the future.

Our next steps for understanding Mars lie in learning how the basaltic shergottite meteorites formed. These are a diverse and richly complex set of rocks, ranging in age from 175 million years to 2.4 billion years or so.

Studying these meteorites in greater detail will help to prepare the next generation of scientists to analyze rocks collected using the Perseverance Rover for the forthcoming NASA Mars Sample Return mission.

James Day, Professor of Geosciences, University of California, San Diego

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Black holes are remarkable astronomical objects with gravity so strong that nothing, not even light, can escape them. The most gigantic ones, known as “supermassive” black holes, can weigh millions to billions times the mass of the Sun.

These giants usually live in the centers of galaxies. Our own galaxy, the Milky Way, contains a supermassive black hole in its heart as well.

So, how do these supermassive black holes become super massive? To answer this question, our team of astrophysicists looked back in time across the universe’s 13.8 billion-year history to track how supermassive black holes have grown from the early days to today.

We constructed a model of the overall growth history of supermassive black holes spanning the past 12 billion years.

How do supermassive black holes grow?

Supermassive black holes grow primarily in two ways. They can consume gas from their host galaxies in a process called accretion, and they can also merge with each other when two galaxies collide.

When supermassive black holes consume gas, they almost always emit strong X-rays, a type of high-energy light invisible to the naked eye. You’ve probably heard of X-rays at the dentist, where they are sometimes used to examine your teeth. The X-rays used by astronomers generally have lower energies than medical X-rays.

So how can any light, even invisible X-rays, escape from black holes? Strictly speaking, the light is not coming from the black holes themselves, but from the gas just outside them. When gas gets pulled toward a black hole, it heats up and shines to produce light, like X-rays. The more gas a supermassive black hole consumes, the more X-rays it will produce.

Thanks to the data accumulated over more than 20 years from three of the most powerful X-ray facilities ever launched into space – Chandra, XMM-Newton and eROSITA – astronomers can capture X-rays from a large number of accreting supermassive black holes in the universe.

This data allows our research team to estimate how fast supermassive black holes grow by consuming gas. On average, a supermassive black hole can consume enough gas to amount to about the mass of the Sun each year, with the exact value depending upon various factors.

For example, the data shows that a black hole’s growth rate, averaged over millions of years, is strongly connected to the mass of all the stars in its host galaxy.

How often do supermassive black holes merge?

Besides feeding on gas, supermassive black holes can also grow by merging with each other to form a single, more massive black hole when galaxies collide.

Supercomputer cosmological simulations can predict about how often these events happen. These simulations aim to model how the universe grows and evolves over time. The countless galaxies flying through space are kind of like bricks, building up the universe.

These simulations show that galaxies and the supermassive black holes they host can undergo multiple mergers across the span of cosmic history.

Our team has tracked these two growth channels – gas consumption and mergers – using X-rays and supercomputer simulations, and then combined them to construct this overall growth history, which maps the growth of black holes across the universe over billions of years.

Our growth history revealed that supermassive black holes grew much faster billions of years ago, when the universe was younger.

Back in the early days, the universe contained more gas for supermassive black holes to consume, and supermassive black holes kept emerging. As the universe aged, the gas was gradually depleted, and supermassive black hole growth slowed. About 8 billion years ago, the number of supermassive black holes stabilized. It hasn’t increased substantially since then.

When there isn’t enough gas available for supermassive black holes to grow by accretion, the only way for them to get larger is through mergers. We didn’t see very many cases of that in our growth history. On average, the most massive black holes can accumulate mass from mergers at a rate up to the mass of the Sun every several decades.

Looking forward

This research has helped us understand how over 90% of the mass in black holes has accumulated over the past 12 billion years.

However, we still need to investigate how they grew in the very early universe to explain the remaining few percentages of the mass in black holes. The astronomical community is starting to make progress exploring these early supermassive black holes, and we hope to find more answers soon.

Fan Zou, Graduate Student in Astronomy and Astrophysics, Penn State and W. Niel Brandt, Professor of Astronomy and Astrophysics, Penn State

This article is republished from The Conversation under a Creative Commons license. Read the original article.