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A few simple questions for climate scientists

Intergovernmental Panel on Climate Change Question 2. Potential impact of global warming Question 4. Warm Up Test your knowledge of global temperature change and its impact on Earth's climate. You scored out of 9. Share your score. True B. Although most locations on the planet have recorded increased temperatures sincechanges in global ocean and atmospheric circulation patterns have created small-scale temperature decreases in a few local regions.

Carbon dioxide B. Nitrogen C. Water vapor D. Heat-trapping greenhouse gases absorb and emit radiation within the thermal infrared range. Water vapor, carbon dioxide and methane are Earth's most abundant greenhouse gases. Nitrogen, which makes up 80 percent of Earth's atmosphere, is not a greenhouse gas. This is because its molecules, which contain two atoms of the same element nitrogenare unaffected by infrared light.

Average precipitation increases B. Average precipitation decreases C. Average precipitation is unchanged. Higher temperatures give rise to a more active water cycle, which means faster and greater evaporation and precipitation and more extreme weather events. In the tropics B. In northern latitudes C. Impacts of global warming are distributed equally all over the planet.

Some of the fastest-warming regions on the planet include Alaska, Greenland and Siberia. These Arctic environments are highly sensitive to even small temperature increases, which can melt sea ice, ice sheets and permafrost, and lead to changes in Earth's reflectance "albedo". Water vapor actually has more heat-trapping power than carbon dioxide. It is also more abundant.

But carbon dioxide and water vapor interact in crucial ways: More carbon dioxide means the atmosphere gets warmer, which then creates more water vapor, which traps heat and warms the atmosphere even more.

Air pollution can take the form of fine particles called "aerosols," which both absorb and scatter the sun's radiation. Both natural and man-made aerosols, such as dust, sea salt, soot and sulfates, affect the climate by reflecting radiation that is transmitted through the atmosphere.

Global temperatures during some of the past interglacial periods have exceeded the average temperatures we observe today, although you would have to go back more than three million years to find a period that was clearly warmer than today. Temperatures in the most recent decade have now exceeded the warmth of the previous Eemian interglacial. The greenhouse effect is a naturally occurring physical process that warms the Earth's surface with energy from the atmosphere.

Without the effect, Earth's average surface temperature would be well below freezing. Using remote sensing from space with satellites B.Climate change is often called a "defining" issue of our time but given its controversy, it can be difficult to understand.

So on Thursday, two of the world's leading scientific groups released a reader-friendly guide. This primer explains why, despite a cold winter in parts of the United States, scientists are so sure that man-made global warming is worsening, and how that's melting Arctic sea ice, raising sea levels and acidifying the oceans. She also said a warmer, moister atmosphere provides more energy for storms and severe weather events.

Even if those emissions suddenly stop, she said it will take thousands of years for the Earth to cool to pre-industrial levels. Co-author Eric Wolff of the University of Cambridge said the planet's climate has changed throughout history but now it's changing 10 times faster, making adaptation more challenging.

He said most of the warming 1. Climate Change: Evidence and Causes is written by a dozen climate scientists on behalf of the U. National Academy of Sciences, a private independent group, and the Royal Society, the national scientific academy of the United Kingdom. It explains what scientists know and what they're still learning, such as the intricacies of clouds. The authors say carbon dioxide CO2 concentrations are now higher than at any time in at leastyears, and unless carbon emissions are curbed, the planet could warm 4.

They answer 20 key questions, 10 of which are excerpted below:.

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How do scientists know that recent climate change is largely caused by human activities? Measurements of different forms of carbon reveal that this increase is because of human activities.

CO2 is already in the atmosphere naturally, so why are emissions from human activity significant? Human activities have significantly disturbed the natural carbon cycle by extracting long-buried fossil fuels and burning them for energy, thus releasing CO2 into the atmosphere.

What role has the sun played in climate change in recent decades? The sun provides the primary source of energy driving Earth's climate system, but its variations have played very little role in the climate changes observed in recent decades. Direct satellite measurements since the late s show no net increase in the sun's output, while at the same time global surface temperatures have increased. Is there a point at which adding more CO2 will not cause further warming?

Adding more CO2 to the atmosphere will cause surface temperatures to continue to increase. As the atmospheric concentrations of CO2 increase, the addition of extra CO2 becomes progressively less effective at trapping Earth's energy, but the surface temperature will still rise.

Does the recent slowdown of warming mean that climate change is no longer happening? Despite the slower rate of warming, the s were warmer than the s. A short-term slowdown in the warming of Earth's surface does not invalidate our understanding of long-term changes in global temperature.

If the world is warming, why are some winters and summers still very cold? Global warming is a long-term trend, but that does not mean that every year will be warmer than the previous one. Day-to-day and year-to-year changes in weather patterns will continue to produce some unusually cold days and nights, and winters and summers, even as the climate warms.Thermometer readings are collected from many thousands of weather stations around the world—over land and ocean—and then used to produce a global average temperature for each year.

The resulting series of annual averages of global temperature from to show that Earth has warmed by 1. These oscillations and other similar phenomena can influence weather and climate patterns around the globe. Earth has warmed by 1. If the globe is still warming, then why are some locations not warming while others have experienced cooling?

The 1. Differences in exposure to sunlight, cloud cover, atmospheric circulation patterns, aerosol concentrations, atmospheric humidity, land surface cover, etc. These differences influence whether and how much a location is warming or cooling.

Can historical temperature data records be trusted? Haven't they been skewed by non-climate factors like instrument changes and "urban heat islands"? Our global historical temperature records can be trusted to represent changes in Earth's temperature over long time periods.

a few simple questions for climate scientists

Different scientific and technical teams in the United States and other countries have assessed weather stations' historical temperature data and concluded that the data are of high quality and are well suited for studies of global temperature changes from to If ignored, non-climate factors can skew individual stations' data records by sometimes introducing an "artificial" cooling trend and sometimes introducing an "artificial" warming trend.

But these and other known problems have not been ignored; rather, steps have been taken to remove or minimize non-climate impacts on the long-term records.

These steps are well documented and have been undertaken in a transparent way. In cases where there is reason to believe that station data contain significant errors that cannot be corrected, those data are removed from national and global averages. Although the possibility of unknown or uncorrected errors in the land surface temperature data cannot be completely excluded, many other lines of evidence confirm that our world has warmed over multiple decades:. A global warming of 1.

Why is this change in global temperature a concern? It's important to recognize that weather and climate are related but they are different things. Daily temperature swings of tens of degrees at a given location are common weather-driven events.

Top 10 climate-change questions: What you need to know

But when measurements of the daily high and low temperatures in many thousands of locations all over the world—on land and ocean—are examined for an entire year and then averaged together, the Earth's annual average temperatures from year to year are found to be very stable when the climate isn't changing. In a geological context, a 1.

a few simple questions for climate scientists

This warming is important because it increases the probabilities of extreme weather and climate events. If global warming were to stop now, its most potentially serious problems would be prevented. However, global warming is expected to continue at an increasing rate. In several decades our world is likely to become warmer than it's been for over a million years, with unpredictable consequences. It's also important to recognize that Earth is not warming uniformly, nor is it expected to.

Middle and high latitudes in general change more than the tropics, and land surface temperatures change more than ocean temperatures. Over the long term, land masses at the latitude of the United States are expected to warm much more than the global average. Yes, human activities have increased the abundance of heat-trapping gases in the atmospherewhich a large majority of climate scientists agree is the main reason for the 1. Carbon dioxide is of greatest concern because its rate of increase is exerting a larger overall warming influence than all of those other gases combined, and because carbon dioxide levels in the atmosphere will remain elevated for centuries unless we implement a way to remove carbon dioxide from the atmosphere effectively and economically.

Most carbon dioxide from human activities is released from burning coal and other fossil fuels. Other human activities, including deforestation, biomass burning, and cement production also produce carbon dioxide.

There is overwhelming scientific evidence that Earth is warming and a preponderance of scientific evidence that human activities are the main cause. Thousands of weather stations worldwide—over land and ocean—have been recording daily high and low temperatures for many decades and, in some locations, for more than a century. When different scientific and technical teams in different U. The primary cause is that, over the last years, human activities have added about billion metric tons of carbon dioxide to the atmosphere, increasing the abundance of this heat-trapping gas by about 40 percent.Starting inCharles Keeling used the scientific method to take meticulous measurements of atmospheric carbon dioxide CO 2 at Mauna Loa Observatory in Waimea, Hawaii.

This graph, known as the Keeling Curve, shows how atmospheric CO 2 has continued rising since then. The scientific method is the gold standard for exploring our natural world. The story goes back to the late s, but infor example, Charles Keeling of the Mauna Loa Observatory in Waimea, Hawaii, started taking meticulous measurements of carbon dioxide CO 2 in the atmosphere, showing the first significant evidence of rapidly rising CO 2 levels and producing the Keeling Curve climate scientists know today.

As you can see, the scientific method is iterative repetitivemeaning that climate scientists are constantly making new discoveries about the world based on the building blocks of scientific knowledge. How does the scientific method work in the real world of climate science? It adds clarity to our way of thinking and shows that scientific knowledge is always evolving.

Note: This is a general illustration of a process that in the real world is often more complex, with the hypothesis often being reformulated several times in light of subsequent experimentation and observations.

A team of engineers in the U. NASA has funded four projects to create virtual portals with biodiversity information for scientists, land managers and decision makers regarding the status of terrestrial ecosystems in a warming world.The issue can be overwhelming.

Global Climate Change

The science is complicated. Predictions about the fate of the planet carry endless caveats and asterisks. This should give you a running start on understanding the problem. As of earlythe Earth had warmed by roughly 2 degrees Fahrenheit, or more than 1 degree Celsius, sincewhen records began at a global scale.

That figure includes the surface of the ocean.

A Climate Scientist Answers Your Extreme Weather Questions

The warming is greater over land, and greater still in the Arctic and parts of Antarctica. The number may sound low. We experience much larger temperature swings in our day-to-day lives from weather systems and from the changing of seasons. But when you average across the entire planet and over months or years, the temperature differences get far smaller — the variation at the surface of the Earth from one year to the next is measured in fractions of a degree.

So a rise of 2 degrees Fahrenheit since the 19th century is actually high. The heat accumulating in the Earth because of human emissions is roughly equal to the heat that would be released byHiroshima atomic bombs exploding across the planet every day. Scientists believe most and probably all of the warming since was caused by the human release of greenhouse gases.

If emissions continue unchecked, they say the global warming could ultimately exceed 8 degrees Fahrenheit, which would transform the planet and undermine its capacity to support a large human population.

The risks are much greater over the long run than over the next few decades, but the emissions that create those risks are happening now.

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This means the current generation of people is dooming future generations to a more difficult future. Over the coming 25 or 30 years, scientists say, the climate is likely to resemble that of today, although gradually getting warmer, with more of the extreme heat waves that can kill vulnerable people. Rainfall will be heavier in many parts of the world, but the periods between rains will most likely grow hotter and drier.

The number of hurricanes and typhoons may actually fall, but the ones that do occur will draw energy from a hotter ocean surface, and therefore may be more intense. Longer term, if emissions continue to rise unchecked, the risks are profound. All of this could take hundreds or even thousands of years to play out, but experts cannot rule out abrupt changes, such as a collapse of agriculture, that would throw civilization into chaos much sooner.

Bolder efforts to limit emissions would reduce these risks, or at least slow the effects, but it is already too late to eliminate the risks entirely. You can reduce your own carbon footprint in lots of simple ways, and most of them will save you money.

You can plug leaks in your home insulation to save power, install a smart thermostat, switch to more efficient light bulbs, turn off the lights in any room where you are not using them, drive fewer miles by consolidating trips or taking public transit, waste less food and eat less meat.

Perhaps the biggest single thing individuals can do on their own is to take fewer airplane trips ; just one or two fewer plane rides per year can save as much in emissions as all the other actions combined. If you want to be at the cutting edge, you can look at buying an electric or hybrid car, putting solar panels on your roof, or both. If you want to offset your emissions, you can buy certificates, with the money going to projects that protect forests, capture greenhouse gases and so forth.

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You can also buy offset certificates in a private marketplace, from companies such as TerraPass ; some people even give these as holiday gifts. In states that allow you to choose your own electricity supplier, you can often elect to buy green electricity; you pay slightly more, and the money goes into a fund that helps finance projects like wind farms.

Leading companies are also starting to demand clean energy for their operations. You can pay attention to company policies, patronize the leaders, and let the others know you expect them to do better. In the end, though, experts do not believe the needed transformation in the energy system can happen without strong state and national policies.By the time fears of an ice age reached the public's attention, there was a long history of concerns about warming.

The idea that burning fossil fuels would warm the planet can be traced back to an paper by Swedish scientist Svante Arrhenius. What was really going on back in the '70s—both in science and in the media? For climate science, the s were a pivotal era. And we were just getting a handle on how sunlight-reflecting aerosol particles behaved in the atmosphere.

Not entirely coincidentally, there was a lull in 20 th century warming between the mids and mids. That same Pacific cycle suppressed global surface temperatures a bit over the past two decades.

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But at the time, the causes of the dip were far from clear. There were also unsettled questions about the strength of competing warming and cooling effects of different types of aerosols—as fossil fuel use continued, which would be more important, the aerosols or the CO 2? The scientific literature at the time shows a field in flux. That led to a conditional statement about future fossil fuel use:.

a few simple questions for climate scientists

If this increased rate of injection of particulate matter in the atmosphere should raise the present global background opacity by a factor of 4, our calculations suggest a decrease in global temperature by as much as 3. Such a large decrease in the average surface temperature of Earth, sustained over a period of [a] few years, is believed to be sufficient to trigger an ice age.

However, by that time, nuclear power may have largely replaced fossil fuels as a means of energy production. Nuclear power may not have replaced fossil fuel use, but pollution controls helped us avoid a world in which aerosols increased so drastically. In fact, a review paper by William Kellogg and the same Stephen Schneider described aerosols only as poorly understood, while pretty accurately estimating 0. The real booster of the cooling predictions was Reid Brysonwho later rejected anthropogenic warming even as global temperatures climbed.

In and papers, Bryson concluded that aerosol cooling would dominate over CO 2 warming—a fact he felt was demonstrated by recent temperatures. There is no indication that these trends will be reversed, and there is some reason to believe that man-made pollution will have an increased effect in the future. But other studies in that same special volume of papers projected warming. One by climate modeling pioneer Syukuro Manabe projected a total of 0. Another by J. Barrett starts by dismissing a rapid warming trend on the grounds that the concentration of CO 2 in the atmosphere was on track to take years to double.

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Like many of these papers, Barrett was trying to build a mathematical model to quantify the cooling influence of aerosols. It therefore appears that the initiation of a glacial epoch by man-made pollutants, while not imminent, is not entirely outside the realm of possibility.

The Discovery of Global Warming [Excerpt]

The thrust of the report was that climate prediction was not yet possible, and it outlined a plan of action for fostering a research program to change that. But it also summarized the state of scientific knowledge at the time. There seems little doubt that the present period of unusual warmth will eventually give way to a time of colder climate, but there is no consensus with regard to either the magnitude or rapidity of the transition.The science is clear: The world is warming dangerously, humans are the cause of it, and a failure to act today will deeply affect the future of the Earth.

Amid the horror and uncertainty of a global health crisis it can be easy to forget that another worldwide disaster is unfolding, although much more slowly. Global warming is happening, and its effects are being felt around the world. The only real debates are over how fast and how far the climate will change, and what society should do — the global-warming equivalents of lockdowns and social distancing — to slow or stop it and limit the damage.

As of now, the damage seems to be getting worse. As I wrote in December, impacts that scientists predicted years ago — including severe storms, heat waves and the melting of glaciers and ice sheets — are accelerating. The coronavirus pandemic can seem overwhelming because of its sheer scope; so can climate change. Since the mids, the Arctic has been warming faster than any other region of the planet: currently, at least two and a half times as fast.

Last year, average air temperatures were about 3. In large part, the Arctic is warming the way the rest of the world warms, only up north the process has run amok. As the concentration of carbon dioxide and other greenhouse gases increase in the atmosphere, so does the amount of heat they trap. But the source of that heat is sunlight striking the Earth, and the amount of heat radiated differs depending on the surface the sunlight hits.

Just as a black car gets much hotter than a white car on a sunny day, darker parts of the planet absorb more sunlight, and in turn radiate more heat, than lighter parts.

The Central Arctic is all ocean — dark water that is covered, to a varying extent, by light ice. The ice absorbs only about 30 to 40 percent of the sunlight hitting it; the rest is reflected. Ocean, on the other hand, absorbs more than 90 percent.

As the Arctic warms more of the ice disappears, leaving more dark ocean to absorb more sunlight and radiate even more heat, causing even more loss of ice. Is this happening at the South Pole as well? No, because while the Arctic is mostly water surrounded by land, Antarctica is the opposite, a huge land mass surrounded by ocean.

Some of the ice that covers the continent is melting, but no dark ocean is being exposed. In the Arctic, currents and winds flow out of the region and affect weather elsewhere. Weakening of the high-altitude winds known as the polar jet stream can bring extra-frigid winter weather to North America and Europe. Cold snaps like these have occurred for a long time although, because of global warming, studies have found that they are not as cold as they used to be. But some scientists now say they think Arctic warming is causing the jet stream to wobble in ways that lead to more extreme weather year round, by creating zones of high-pressure air that can cause weather systems — the ones that bring extreme heat, for example — to stall.

Arctic warming may also be affecting climate over the longer term.

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These salinity changes may eventually have an effect on some of the large ocean currents that help determine long-term climate trends in parts of the world. The second warmest year on record wasand it closed out the hottest recorded decade. Ocean temperatures are risingtoo, hitting a high in as well, and increasing faster than previously estimated. But scientists can also look back even further to figure out temperatures on Earth before any humans were alive.

Instruments like it, together with the GPS-connected devices in the global Argo floats network, are how researchers monitor ocean temperatures. For annual temperature reports, scientists rely on a historical temperature record — someone or some machine taking daily temperatures. This is how we know, for example, that was hotter than But the temperature record only stretches back to the s for much of the world, and has some gaps.

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