were introduced about 10,000 years ago. Because hunter-gatherers have fared poorly in comparison with their agricultural cousins, their numbers have dwindled, and they have been forced to live in marginal environments, such as deserts and arctic wastelands. In higher latitudes, the shorter growing seasons have restricted the availability Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 33 to 37. Some time ago, scientists began experiments to find out (33)______ it would be possible to set up a "village" under the sea. A special room was built and lowered (34)______ the water of Port Sudan in the Red Sea. For 29 days, five men lived at Tuskegee Home The Tuskegee Timeline In 1932, the USPHS, working with the Tuskegee Institute, began a study to record the natural history of syphilis. It was originally called the "Tuskegee Study of Untreated Syphilis in the Negro Male" (now referred to as the "USPHS Syphilis Study at Tuskegee"). So began the Monks Wood Wilderness experiment, which is now 60 years old. A rewilding study before the term existed, it shows how allowing land to naturally regenerate can expand native woodland and help tackle climate change and biodiversity loss. How new woodland generates itself. A shrubland of thorn thickets emerged after the first 10 to 15 the tuskegee study of untreated syphilis in the negro male [1] [2] [3] (informally referred to as the tuskegee experiment or tuskegee syphilis study) was a study conducted between 1932 and 1972 by the united states public health service (phs) and the centers for disease control and prevention (cdc) on a group of nearly 400 african americans with … Some time ago, scientists began experiments to find out whether it would be possible to set up a "village" under the sea. A special room was built and lowered into the water of Port Sudan in the Red Sea. For 29 days, five men lived at a depth of 40 feet. At a much lower level, another two divers stayed for a week in a smaller "house". JKsH. A fossil collector since childhood, Bob Hazen has come up with new scenarios for life's beginnings on earth billions of years ago. Amanda Lucidon A hilly green campus in Washington, houses two departments of the Carnegie Institution for Science the Geophysical Laboratory and the quaintly named Department of Terrestrial Magnetism. When the institution was founded, in 1902, measuring the earth’s magnetic field was a pressing scientific need for makers of nautical maps. Now, the people who work here—people like Bob Hazen—have more fundamental concerns. Hazen and his colleagues are using the institution’s “pressure bombs”—breadbox-size metal cylinders that squeeze and heat minerals to the insanely high temperatures and pressures found inside the earth—to decipher nothing less than the origins of life. Hazen, a mineralogist, is investigating how the first organic chemicals—the kind found in living things—formed and then found each other nearly four billion years ago. He began this research in 1996, about two decades after scientists discovered hydrothermal vents—cracks in the deep ocean floor where water is heated to hundreds of degrees Fahrenheit by molten rock. The vents fuel strange underwater ecosystems inhabited by giant worms, blind shrimp and sulfur-eating bacteria. Hazen and his colleagues believed the complex, high-pressure vent environment—with rich mineral deposits and fissures spewing hot water into cold—might be where life began. Hazen realized he could use the pressure bomb to test this theory. The device technically known as an “internally heated, gas media pressure vessel” is like a super-high-powered kitchen pressure cooker, producing temperatures exceeding 1,800 degrees and pressures up to 10,000 times that of the atmosphere at sea level. If something were to go wrong, the ensuing explosion could take out a good part of the lab building; the operator runs the pressure bomb from behind an armored barrier. In his first experiment with the device, Hazen encased a few milligrams of water, an organic chemical called pyruvate and a powder that produces carbon dioxide all in a tiny capsule made of gold which does not react with the chemicals inside that he had welded himself. He put three capsules into the pressure bomb at 480 degrees and 2,000 atmospheres. And then he went to lunch. When he took the capsules out two hours later, the contents had turned into tens of thousands of different compounds. In later experiments, he combined nitrogen, ammonia and other molecules plausibly present on the early earth. In these experiments, Hazen and his colleagues created all sorts of organic molecules, including amino acids and sugars—the stuff of life. Hazen’s experiments marked a turning point. Before them, origins-of-life research had been guided by a scenario scripted in 1871 by Charles Darwin himself “But if and oh! what a big if! we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc., present, that a proteine compound was chemically formed ready to undergo still more complex changes....” In 1952, Stanley Miller, a graduate student in chemistry at the University of Chicago, attempted to create Darwin’s dream. Miller set up a container holding water representing the early ocean connected by glass tubes to one containing ammonia, methane and hydrogen—a mixture scientists of the day thought approximated the early atmosphere. A flame heated the water, sending vapor upward. In the atmosphere flask, electric sparks simulated lightning. The experiment was such a long shot that Miller’s adviser, Harold Urey, thought it a waste of time. But over the next few days, the water turned deep red. Miller had created a broth of amino acids. Forty-four years later, Bob Hazen’s pressure bomb experiments would show that not just lightning storms but also hydrothermal vents potentially could have sparked life. His work soon led him to a more surprising conclusion the basic molecules of life, it turns out, are able to form in all sorts of places near hydrothermal vents, volcanoes, even on meteorites. Cracking open space rocks, astrobiologists have discovered amino acids, compounds similar to sugars and fatty acids, and nucleobases found in RNA and DNA. So it’s even possible that some of the first building blocks of life on earth came from outer space. Hazen’s findings came at an auspicious time. “A few years before, we would have been laughed out of the origins-of-life community,” he says. But NASA, then starting up its astrobiology program, was looking for evidence that life could have evolved in odd environments—such as on other planets or their moons. “NASA [wanted] justification for going to Europa, to Titan, to Ganymede, to Callisto, to Mars,” says Hazen. If life does exist there, it’s likely to be under the surface, in warm, high-pressure environments. Back on earth, Hazen says that by 2000 he had concluded that “making the basic building blocks of life is easy.” A harder question How did the right building blocks get incorporated? Amino acids come in multiple forms, but only some are used by living things to form proteins. How did they find each other? In a windowed corner of a lab building at the Carnegie Institution, Hazen is drawing molecules on a notepad and sketching the earliest steps on the road to life. “We’ve got a prebiotic ocean and down in the ocean floor, you’ve got rocks,” he says. “And basically there’s molecules here that are floating around in solution, but it’s a very dilute soup.” For a newly formed amino acid in the early ocean, it must have been a lonely life indeed. The familiar phrase “primordial soup” sounds rich and thick, but it was no beef stew. It was probably just a few molecules here and there in a vast ocean. “So the chances of a molecule over here bumping into this one, and then actually a chemical reaction going on to form some kind of larger structure, is just infinitesimally small,” Hazen continues. He thinks that rocks—whether the ore deposits that pile up around hydrothermal vents or those that line a tide pool on the surface—may have been the matchmakers that helped lonely amino acids find each other. Rocks have texture, whether shiny and smooth or craggy and rough. Molecules on the surface of minerals have texture, too. Hydrogen atoms wander on and off a mineral’s surface, while electrons react with various molecules in the vicinity. An amino acid that drifts near a mineral could be attracted to its surface. Bits of amino acids might form a bond; form enough bonds and you’ve got a protein. Back at the Carnegie lab, Hazen’s colleagues are looking into the first step in that courtship Kateryna Klochko is preparing an experiment that—when combined with other experiments and a lot of math—should show how certain molecules stick to minerals. Do they adhere tightly to the mineral, or does a molecule attach in just one place, leaving the rest of it mobile and thereby increasing the chances it will link up to other molecules? Klochko gets out a rack, plastic tubes and the liquids she needs. “It’s going to be very boring and tedious,” she warns. She puts a tiny dab of a powdered mineral in a four-inch plastic tube, then adds arginine, an amino acid, and a liquid to adjust the acidity. Then, while a gas bubbles through the solution, she waits...for eight minutes. The work may seem tedious indeed, but it takes concentration. “That’s the thing, each step is critical,” she says. “Each of them, if you make a mistake, the data will look weird, but you won’t know where you made a mistake.” She mixes the ingredients seven times, in seven tubes. As she works, “The Scientist” comes on the radio “Nooooobody saaaaid it was easyyyy,” sings Coldplay vocalist Chris Martin. After two hours, the samples go into a rotator, a kind of fast Ferris wheel for test tubes, to mix all night. In the morning, Klochko will measure how much arginine remains in the liquid; the rest of the amino acid will have stuck to the mineral powder’s tiny surfaces. She and other researchers will repeat the same experiment with different minerals and different molecules, over and over in various combinations. The goal is for Hazen and his colleagues to be able to predict more complex interactions, like those that may have taken place in the earth’s early oceans. How long will it take to go from studying how molecules interact with minerals to understanding how life began? No one knows. For one thing, scientists have never settled on a definition of life. Everyone has a general idea of what it is and that self-replication and passing information from generation to generation are key. Gerald Joyce, of the Scripps Research Institute in La Jolla, California, jokes that the definition should be “something like that which is squishy.’” Hazen’s work has implications beyond the origins of life. “Amino-acids-sticking-to-crystals is everywhere in the environment,” he says. Amino acids in your body stick to titanium joints; films of bacteria grow inside pipes; everywhere proteins and minerals meet, amino acids are interacting with crystals. “It’s every rock, it’s every soil, it’s the walls of the building, it’s microbes that interact with your teeth and bones, it’s everywhere,” Hazen says. At his weekend retreat overlooking the Chesapeake Bay, Hazen, 61, peers through binoculars at some black-and-white ducks bobbing around in circles and stirring the otherwise still water. He thinks they’re herding fish—a behavior he’s never seen before. He calls for his wife, Margee, to come take a look “There’s this really interesting phenomenon going on with the buffleheads!” Living room shelves hold things the couple has found nearby beach glass, a basketful of minerals, and fossilized barnacles, coral and great white shark teeth. A 15-million-year-old whale jawbone, discovered on the beach at low tide, is spread out in pieces on the dining room table, where Hazen is cleaning it. “It was part of a living, breathing whale when this was a tropical paradise,” he says. Hazen traces his interest in prehistory to his Cleveland childhood, growing up not far from a fossil quarry. “I collected my first trilobite when I was 9 or 10,” he says. “I just thought they were cool,” he says of the marine arthropods that went extinct millions of years ago. After his family moved to New Jersey, his eighth-grade science teacher encouraged him to check out the minerals in nearby towns. “He gave me maps and he gave me directions and he gave me specimens, and my parents would take me to these places,” says Hazen. “So I just got hooked.” After taking a paleontology class together at the Massachusetts Institute of Technology, Hazen and Margee Hindle, his future wife, started collecting trilobites. They now have thousands. “Some of them are incredibly cute,” says Hazen. “This bulbous nose—you want to hug them.” There are trilobites all over Hazen’s office and a basement guest room at the Hazens’ Bethesda, Maryland, home—they cover shelves and fill desk drawers and cabinets. There’s even trilobite art by his now grown children, Ben, 34, who is studying to be an art therapist, and Liz, 32, a teacher. “This is the ultimate cute trilobite,” he says, reaching into a cabinet and taking out a Paralejurus. “How can you not love that?” Hazen calls himself a “natural collector.” After he and Margee bought a picture frame that just happened to hold a photograph of a brass band, they started buying other pictures of brass bands; eventually they wrote a history of brass bands—Music Men—and a time in America when almost every town had its own. Bob has played trumpet professionally since 1966. He has also published a collection of 18th-and 19th-century poems about geology, most of which, he says, are pretty bad “And O ye rocks! schist, gneiss, whate’er ye be/Ye varied strata, names too hard for me”. But the couple tend not to hold on to things. “As weird as this sounds, as a collector, I’ve never been acquisitive,” Bob says. “To have been able to hold them and study them up close is really a privilege. But they shouldn’t be in private hands.” Which is why the Hazen Collection of Band Photographs and Ephemera, ca. 1818-1931, is now at the National Museum of American History. Harvard has the mineral collection he started in eighth grade, and the Hazens are in the process of donating their trilobites to the National Museum of Natural History. After considering, for some time, how minerals may have helped life evolve, Hazen is now investigating the other side of the equation how life spurred the development of minerals. He explains that there were only about a dozen different minerals—including diamonds and graphite—in dust grains that pre-date the solar system. Another 50 or so formed as the sun ignited. On earth, volcanoes emitted basalt, and plate tectonics made ores of copper, lead and zinc. “The minerals become players in this sort of epic story of exploding stars and planetary formation and the triggering of plate tectonics,” he says. “And then life plays a key role.” By introducing oxygen into the atmosphere, photosynthesis made possible new kinds of minerals—turquoise, azurite and malachite, for example. Mosses and algae climbed onto land, breaking down rock and making clay, which made bigger plants possible, which made deeper soil, and so on. Today there are about 4,400 known minerals—more than two-thirds of which came into being only because of the way life changed the planet. Some of them were created exclusively by living organisms. Everywhere he looks, Hazen says, he sees the same fascinating process increasing complexity. “You see the same phenomena over and over, in languages and in material culture—in life itself. Stuff gets more complicated.” It’s the complexity of the hydrothermal vent environment—gushing hot water mixing with cold water near rocks, and ore deposits providing hard surfaces where newly formed amino acids could congregate—that makes it such a good candidate as a cradle of life. “Organic chemists have long used test tubes,” he says, “but the origin of life uses rocks, it uses water, it uses atmosphere. Once life gets a foothold, the fact that the environment is so variable is what drives evolution.” Minerals evolve, life arises and diversifies, and along come trilobites, whales, primates and, before you know it, brass bands. Helen Fields has written about snakehead fish and the discovery of soft tissue in dinosaur fossils for Smithsonian. Amanda Lucidon is based in Washington, / To mimic conditions for life on early earth, Bob Hazen, in his Carnegie lab, used a "pressure bomb" to heat and compress chemicals. Amanda Lucidon / A fossil collector since childhood, Hazen, shown here inspecting ancient seashells on Chesapeake Bay, has come up with new scenarios for life's beginnings on earth billions of years ago. Amanda Lucidon / Scientists are searching for life's origins beyond the "warm little pond" that, 140 years ago, Charles Darwin speculated was the starting place. Kateryna Klochko, in Hazen's lab, combines mineral dust and amino acids, the building blocks of proteins. Amanda Lucidon / Some meteorites, shown here is a magnified cross section of one found in Chile, contain amino acids, raising the possibility that life was seeded from space. Amanda Lucidon / Despite high temperatures and pressures, deep-sea hydrothermal vents harbor living things. Science Source / Hazen began collecting trilobites—extinct marine arthropods like this Paralejurus—when he was a child. Amanda Lucidon / The first organic molecules may have needed rocks to bring them together, says Hazen, with his wife Margee near their Chesapeake Bay weekend retreat. But the relationship goes both ways once living things were established, they created new minerals. Amanda Lucidon Get the latest Science stories in your inbox. Recommended Videos Filed Under Earth Science History of Climate Change Interactive Timeline The tables below contain all of the items that are in the timeline above, organized by category greenhouse gases, modeling, past climate, impacts of climate change, and climate reports. If you have suggestions for additions to this timeline of the History of Climate Science Research, please contact us. Greenhouse Gases and the Greenhouse Effect Date Event 1640 Carbon Dioxide Discovered Johann Baptista van Helmolt, Flemish alchemist, determined that air is a mixture of gases. He studied carbon dioxide, which he called the “spirit of wood” because it was given off when wood was burned. In an experiment, he burned coal to see how much carbon dioxide it added to the air. 1754 First Carbon Dioxide Detector Joseph Black, a medical student in Edinburgh, figured out that limewater can be used as a carbon dioxide CO2 detector. He observed that the normally clear liquid turned milky when exposed to "fixed air," which is what he called CO2. He started measuring the gas everywhere with his limewater, and found that it was released from mineral water, fermenting yeast, burning coal and oil, cremating corpses, and human exhalation. The limewater instrument was later improved by Lord Cavendish, and became known as the Cavendish Apparatus. Learn more The Discovery of the Greenhouse Effect 1760 Industrial Revolution Begins Since the start of the Industrial Revolution, the way people live and work has changed dramatically as manufacturing expanded. Over time, the amount of fossil fuels burned increased, which has increased the amount of carbon dioxide CO2 in the atmosphere . Before the Industrial Revolution, there was approximately 280 parts per million ppm of CO in the air. Today, that amount is over 400 ppm. 1824 Describing Earth's Atmosphere as a Greenhouse Jean-Baptiste-Joseph Fourier, a mathematician working for Napoleon, was the first to describe how Earth's atmosphere retains warmth on what would otherwise be a very cold planet.. To help explain the concept, he compared the atmosphere to the glass walls of a greenhouse. Learn more The Discovery of the Greenhouse Effect 1856 Discovering Gases That Trap Heat Eunice Foote, American scientist, discovered that carbon dioxide and water vapor cause air to warm in sunlight. In 1856, she presented her findings at the meeting of the American Association for the Advancement of Science AAAS. “A paper was read before the late meeting of the Scientific Association, by Prof. Henry for Mrs. Eunice Foot, detailing her experiments to determine the effects of the sun’s rays on different gases,” noted an 1856 article in Scientific American. 1859 Testing the Heat-Trapping Ability of Gases John Tyndall, British physicist, tested the gases in the atmosphere to find out which are responsible for the greenhouse effect. He found that nitrogen and oxygen, which make up almost all of the atmosphere, have no ability to trap heat, but that three gases present in smaller quantities do carbon dioxide, ozone, and water vapor. Tyndall speculated that if the amounts of these gases dropped, it would chill the Earth. 1896 Connecting Coal, Carbon Dioxide, and Climate Swedish chemist Svante Arrhenius recognized that burning coal could increase carbon dioxide and warm the climate. He estimated how much carbon dioxide the ocean could absorb. In an 1896 lecture, Arrhenius noted that it was not yet possible to calculate how fast temperature was rising. He also speculated that warming would be beneficial as people in the future "might live under a milder sky and in less barren surroundings." Learn more Svante Arrhenius and the Greenhouse Effect [.pdf] 1938 Increasing Carbon Dioxide and Increasing Temperatures British coal engineer George Callendar compiled all carbon dioxide measurements made over the previous 100 years and found that the amount of CO2 was increasing. He also found that temperatures were rising. His conclusion was that this was a good thing, that "the return of the deadly glaciers should be delayed indefinitely." Read his 1949 article Can Carbon Dioxide Influence Climate? 1957 Our Unintended Experiment Roger Revelle, oceanographer, and Hans Suess, Austrian-born chemist, realizing that carbon dioxide from industrial sources must be building up in the atmosphere, wrote in 1957 "Thus human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future." 1958 Climate Science on Television The Bell Telephone Science Hour addressed how our actions could be changing Earth's climate. "Even now, [we] may be unwittingly changing the world's climate through the waste products of [our] civilization," said the narrator. "Due to our release from factories and automobiles every year of more than six billion tons of carbon dioxide, which helps the air absorb heat from the Sun, our atmosphere seems to be getting warmer." 1958 Daily Measurements of Carbon Dioxide Charles Keeling started making daily measurements of the amount of carbon dioxide in the air atop Mauna Loa in Hawaii. That first March day, he found 313 parts per million ppm of carbon dioxide in the air. The measurements, which are still make each day, reached 400 ppm on May 9, 2013, and continue to climb. 1988 Climate in Congress NASA climate scientist James Hansen testified before the Senate Energy and Natural Resources Committee stating that climate was warming, greenhouse gases are responsible for the warming, and we are responsible for the growth in these gases. 1992 An Increasingly Acidic Ocean scientists Stephen V. Smith and Buddemeier pointed out that more carbon dioxide CO2 in the ocean could be a problem for coral reefs. Later experiments confirmed their hypothesis that CO2 makes seawater slightly acidic, which makes it difficult for corals and other animals to build reefs. Today at NCAR, scientist Joanie Kleypas builds on their work, researching the impacts of acidic oceans on marine life. 2016 CO2 Stays Above 400 ppm Year-round September is typically when carbon dioxide is at a minimum in its annual cycle. September 2016 was the first time that minimum level was over 400 parts per million. Before large-scale burning of fossil fuels, CO2 levels were about 280 ppm. Learn more The World Passes 400 PPM Threshold. Permanently Modeling the Earth and Future Climate Date Event 1960s Simple Models to Study the Atmosphere Syukuro Manabe and Richard Wetherald developed a basic model of the atmosphere at NOAA. With the model, they found that more carbon dioxide in the atmosphere causes higher temperatures at Earth's surface. This simple model was the first step toward development of complex Earth system models. Read their 1967 paper Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity “Greenhouse gases are the second most important factor for climate, after the Sun.” -Syukuro Manabe 1960s Modeling the Whole Atmosphere At the National Center for Atmospheric Research, scientists Akira Kasahara and Warren Washington developed a model of the whole atmosphere called a general circulation model. At first, they ran the model on a CDC 3600, a computer that filled a room yet only had a single processor. “We pretty much beat the thing up because we were running a general circulation model on it 24 hours a day, seven days a week,” said Washington. “They didn’t anticipate for people to use computers in that way.” Learn more NCAR's CDC 3600 1975-1985 Better Models and Faster Computers More powerful supercomputers like the Cray 1A allowed researchers to develop more complex models that included the dynamics of both the atmosphere and ocean. Their results confirmed those from earlier models climate is warming because of the greenhouse gases added to the atmosphere. Learn more NCAR's Cray 1A 1990s Climate System Models New models were developed to include how the ocean, land, sea ice, and atmosphere interact to affect the climate. At the end of the decade, the National Center for Atmospheric Research ran a new model, the Community Climate System Model CCSM, on its latest supercomputer to learn more about interactions in Earth's climate system. Learn more 1998 special issue on CCSM results in the Journal of Climate 1990 Regional Climate Modeling Robert Dickinson led a team to create a regional climate model for the western United States in 1989 and, in 1990, Filippo Giorgi simulated regional climate using a model nested in a general circulation model GCM. Regional climate modeling has allowed predictions of how global climate change impacts local areas. Learn more Thirty years of regional climate modeling 2010 Earth System Models Provide Improved Understanding Models that can include dynamics of the Earth system, including feedbacks and biogeochemical cycling, gave a more detailed view of climate change and its impacts. Advancements in modeling at NCAR, NOAA, and other research centers around the world have ushered in a new era in understanding of our complex planet. Learn more Community Earth System Model at NCAR NOAA’s First Earth System Model 2020 Climate Models are Getting Future Warming Projections Right Climate models have been making predictions since the 1970s, but are the predictions right? To find out, scientists ran 17 global climate models and compared the results with observed temperatures over the past half-century. Fourteen of the models predicted past temperatures accurately, which gives scientists confidence in the models’ ability to correctly project future warming. Learn more Climate Models are Getting Future Warming Right Studying Past Climate Date Event 1891 Climate Recorded in Dust Self-taught geologist John Hardcastle realized that large deposits of wind-blown dust known as loess in New Zealand record changes in climate from Ice Ages to warm periods in between. "This growing dust heap played the part of an observant bystander, taking notes of certain climatic phenomena as they successively arose." —John Hardcastle Learn more John Hardcastle on Glacier Motion and Glacial Loess 1966 Ice Core Uncovers 8,200 Years of Climate At Camp Century, Greenland, an ice core was extracted that showed 8,200 years of annual snow accumulation as thin layers in the ice. The thin layers of ice allowed scientists to reconstruct ancient climate using an ice core for the first time. Learn more Core of climate history 1966 Climate History from the Ocean Floor In 1966, a shipbuilding company began making a ship with a drill rig on top for the Deep Sea Drilling Project, a project based at the Scripps Institute of Oceanography in San Diego, California. The drill rig would allow scientists to collect cores from the ocean floor around the world that contain layers of sediments – a record of ancient changes in climate over millions of years. Today the Integrated Ocean Drilling Program continues to collect these deepsea records. Learn more Integrated Ocean Drilling Program 1985 Drilling 150,000 Years Deeper into the Ice Ice cores extracted from Antarctic ice in 1985 showed carbon dioxide and temperature had gone up and down together in wide swings over the past 150,000 years, the same relationship that computer models suggested. Learn more Core of climate history 2005 Finding Really Old Ice and its Climate History A deep ice core from East Antarctica helped us understand how climate has changed over the past 650,000 years. Studying ancient air bubbles in the ice, scientists have learned details about the ancient atmosphere, including that levels of carbon dioxide are unusually high today compared to past interglacial periods. Learn more Core of climate history 2012 Indigenous Climate Knowledge Since 2012, the Rising Voices program has brought indigenous knowledge and western science together to improve understanding of climate change and other types of science and to develop strategies for resilient and sustainable communities. "We need to appreciate the experience and knowledge that has been transferred from generation to generation to generation in Native American communities." - Bob Gough Learn more Rising Voices at NCAR The Science of Climate Impacts Date Event 1950s Shrinking Arctic Sea Ice Measurements since the 1950s indicate that the amount of sea ice in the Arctic has been declining. The Arctic is projected to have no summer ice cover by the middle of this century. Check on sea ice at the National Snow and Ice Data Center. 1950s-1970s Air Pollution Dampens Warming Aerosols, emitted into the atmosphere from smokestacks and tailpipes, caused a slight cooling of climate, which fueled speculation that we could enter an Ice Age. As countries passed clean air legislation, aerosol pollution decreased and climate warming continued. 2003 Heat Wave Linked to Climate Change Researchers determined that climate change played a large role in the 2003 heatwave in Europe, which resulted in more than 30,000 deaths. Learn more European Summer Heat Wave of 2003 2006 Economic Impacts of Climate Change The Stern Review described the economic impacts of climate change, finding that mitigating reducing the amount of greenhouse gas emissions and adapting making changes to the way we live would be much less expensive than the cost of trying to recover from the disastrous impacts of climate change in the future. Read the report The Stern Review on the Economics of Climate Change 2007-2008 Studying Impacts in the Polar Regions During International Polar Year which was actually two years' long 2007-2008, scientists documented numerous impacts of climate change on the polar regions, which are warming more rapidly than other areas of Earth. Impacts included melting ice, thawing permafrost, and changes in ecosystems. They found that changes were especially pronounced in the Arctic. 2011 The Effect of Climate Change on Extreme Weather A new branch of climate science, called attribution research, formed to study how global climate change affects extreme weather events such as heat waves, hurricanes, floods, and droughts. Each year since 2011, the Bulletin of the American Meteorological Society has issued a special report about extreme weather events during the past year and how the risk of severe weather has been altered by climate change. Read the report Explaining Extreme Events from a Climate Perspective 2019 Dwindling Biodiversity With Earth system models, scientists are now able to study how species and ecosystems around the world are likely to be affected by climate change and other human impacts. According to a 2019 United Nations report, climate change and other human impacts such as pollution and land use are threatening species worldwide. "Around 1 million species already face extinction, many within decades, unless action is taken," according to the report. Read the report United Nations 2019 Report Learn how NCAR is modeling Western Pacific coral reefs 2021 2020 Ties with 2016 as the Warmest Year On Record 2016 and 2020 tied as the warmest years on record, according to 2021 reports. Scientists studying long-term temperature records found that the 10 warmest years through 2020 all occurred since 2000. From NASA Goddard Institute for Space Studies Director Gavin Schmidt, “...As the human impact on the climate increases, we have to expect that records will continue to be broken.“ Learn more Read the article NASA Global Temperature Analysis More information Global Temperature Rankings The Intergovernmental Panel on Climate Change IPCC Date Event 1988 The Intergovernmental Panel on Climate Change IPCC Formed The IPCC was formed by the World Meteorological Organization and the United Nations to review the latest climate science every few years and help governments around the world understand what we know about climate change, its impacts, and efforts to adapt and mitigate. Learn more About the IPCC 1990 First Climate Assessment Report by the IPCC Published in 1990, the IPCC's First Assessment Report stated that it was certain that "human activities are substantially increasing the atmospheric concentrations of greenhouse gases."According to the report, greenhouse gas increases had caused temperature to increase by to Celsius - Fahrenheit over the past century and would cause global average temperature to warm about 1°C by 2025 and 3°C by 2100. Projections for regional temperature and precipitation changes were highly uncertain. Learn more Read the Overview of the IPCC First Assessment Report [.pdf] 1995 Evidence Suggests Human Influence on Climate The Second Assessment Report of the IPCC provided key information that led to the development of the Kyoto Protocol in 1997."Considerable progress has been made in the understanding of climate change science since 1990," wrote the authors. Acknowledging that global climate had changed over the past century, the authors noted that regional climate change was also evident and that "global sea level has risen by 10 - 25 centimeters 4-10 inches over the past 100 years." Learn more About the Kyoto Protocol 2001 New and Stronger Evidence That We Are Causing Climate Change According to the Third Assessment Report of the Intergovernmental Panel on Climate Change IPCC, "there is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities." Climate models projected that, between 1990 and 2100, Earth's atmosphere would warm by to to depending on how much greenhouse gas humans emitted during that time. "The projected rate of warming is very likely to be without precedent during at least the last 10,000 years," noted the authors. The report outlined the impacts of warming, such as changing precipitation patterns, melting glaciers, and rising sea levels, as well as changes to biodiversity, economic systems, and human health. 2007 Climate Change Indisputable The IPCC Fourth Assessment Report noted that human-caused greenhouse gas emissions had increased 70% between 1970 and 2004 and the effects of climate change were becoming apparent. "Warming of the climate system is unequivocal," wrote the authors of the 2007 report, "as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level." "Anthropogenic [human-caused] warming could lead to some impacts that are abrupt or irreversible," they warned. "More extensive adaptation than is currently occurring is required to reduce vulnerability to climate change." 2014 Emissions Are the Highest in History The IPCC 5th Assessment Report noted that our influence on climate is clear and "recent anthropogenic emissions of greenhouse gases are the highest in history." The report's findings led to the Paris Climate Accord, in which nearly all of the world's countries 174 countries in total committed to actions limiting warming to below 2° Celsius Fahrenheit in an effort to avoid the most catastrophic impacts. The United States announced in 2017 that it would back out of the agreement. Learn more Paris Climate Accord 2022 Adverse Impacts are Beyond Natural Climate Variability The Sixth Assessment Report highlights the impacts of human-induced climate change, including more frequent and intense extreme events. The changes have caused widespread adverse impacts and damages to nature and people, beyond what would be expected from natural climate variability. Learn more IPCC Summary for Policymakers Headline Statements In 1952, atomic scientists came together on the 10th anniversary of the first controlled nuclear fission chain reaction, which took place Dec. 2, 1942, at the University of Chicago. Courtesy of University of Chicago Photographic Archive hide caption toggle caption Courtesy of University of Chicago Photographic Archive In 1952, atomic scientists came together on the 10th anniversary of the first controlled nuclear fission chain reaction, which took place Dec. 2, 1942, at the University of Chicago. Courtesy of University of Chicago Photographic Archive Seventy-five years ago this week, scientists from the University of Chicago created the first controlled, self-sustained nuclear chain reaction, a feat that was essential in the development of an atomic bomb during World War II. Enrico Fermi and his team of physicists secretly conducted the Chicago Pile 1 experiment on a squash court under the stands of a football stadium on Dec. 2, 1942. The anniversary of this unprecedented achievement comes as tensions escalate between the and North Korea, which launched a new ballistic missile on Tuesday. The 1942 test was a crucial first step in the creation of nuclear weapons by the endeavor known as the Manhattan Project, says Eric Isaacs, executive vice president of research, innovation and national laboratories at the University of Chicago. "The way I like to think about it is It was not enough to power a light bulb, but it changed the world," he tells Here & Now's Jeremy Hobson. "It changed, obviously, the world because the war ended some years later with the bomb." Enrico Fermi, a professor of physics at the University of Chicago and the winner of the 1938 Nobel Prize in physics, led the team of scientists which succeeded in obtaining the first controlled, self-sustaining nuclear chain reaction on Dec. 2, 1942. Courtesy of Argonne National Laboratory hide caption toggle caption Courtesy of Argonne National Laboratory The coordinated effort to harness nuclear energy began in 1939 after scientists in Europe demonstrated fission of a nucleus for the first time, Isaacs explains. Many scientists in the were expatriates, some of whom were refugees from fascist Europe, and they quickly realized the potential that Germany could build a bomb. According to NPR contributor Marcelo Gleiser, Hungarian physicist Leó Szilárd first proposed the idea of a nuclear chain reaction, "whereby neutrons released from radioactive atomic nuclei would hit other heavy nuclei causing them to split fission into smaller nuclei. Every time this splitting happened, a little bit of energy was released. "Szilárd knew that the possibility of a chain reaction represented a shift in world history," Gleiser, a professor of physics at Dartmouth College, writes. "An explosive device with an uncontrolled chain reaction would have devastating consequences." A group of scientists persuaded Albert Einstein, the most famous scientist of the day, to write President Franklin Roosevelt urging him to launch a major bomb-making effort. The letter essentially said, "If we don't build a bomb, Germany will first." Fermi's pile experiment, which served as the framework for modern nuclear reactors, generated only about a half watt of power, University of Pennsylvania physics and astronomy professor Gino Segre writes in the Chicago Tribune The experiment focused on a crude pile — a 20-foot-high structure made of close to 40,000 graphite bricks, weighing 20 pounds each and embedded with a total of almost 100,000 pounds of uranium. Thirteen-foot control rods, ready to be pushed in or out depending on the neutron count, protruded from the pile. Fermi, cool and collected throughout the experiment, gave orders from the balcony above the squash court. The 49 attending scientists and observers fully trusted this Nobel Prize winner, called the "Pope of Physics" by his admiring peers because of his scientific infallibility. At 325 in the afternoon, after ordering the last control rod to be pulled halfway out, Fermi announced the pile had "gone critical." The chain reaction gradually accelerated, reaching dangerous levels ever more quickly. After the neutron count dramatically intensified at 349 Fermi continued to run the pile for nearly 5 minutes before calling a halt to the experiment. But those minutes marked the beginning of a new era. A drawing of Chicago Pile 1, the nuclear reactor that scientists used to achieve the first controlled, self-sustaining chain reaction on Dec. 2, 1942. Courtesy of Argonne National Laboratory hide caption toggle caption Courtesy of Argonne National Laboratory A drawing of Chicago Pile 1, the nuclear reactor that scientists used to achieve the first controlled, self-sustaining chain reaction on Dec. 2, 1942. Courtesy of Argonne National Laboratory While the reaction only produced a small amount of energy, Isaacs says the event was a "remarkable engineering feat" that dramatically changed the landscape of science. Three years later, the dropped the first atomic bomb on the Japanese city of Hiroshima. Despite the unprecedented destruction created by the bomb, Isaacs says nuclear power plants, as well as other nuclear materials, wouldn't exist without Fermi's experiment. The experiment demonstrated that generating "nuclear power releasing the energy of one nucleus is not nearly enough," Isaacs explains. "You have to re-release the energy of many, many nuclei to create the kind of energy that are required for nuclear-produced electricity." At a time when there is rising concern about the temperament of world leaders in control of nuclear weapons, Isaacs says the scientists who worked on the pile experiment "realized the devastating consequences of the kind of energy they could release with fission." But the fear that drove them to move forward, Isaacs says, fundamentally changed the role of science in our society. "There were very loud debates going on amongst the scientists about whether we should use a bomb, whether we shouldn't use a bomb, how it should be done," he says, "and in fact, out of World War II, one of the things that emerged was the engagement of scientists in discussions around policy." Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word for each of the blanks from 1 to time ago, scientists began experiments to find out 1______ it would be possible to set up a “village” under the sea. A special room was built and lowered 2______ the water of Port Sudan in the Red Sea. For 29 days, five men lived at a depth of 40 feet. At a 3______ lower level, another two divers stayed for a week in a smaller “house”. On returning to the surface, the men said that they had experienced no difficulty in breathing and had 4______ many interesting scientific observations. The captain of the party, Commander Cousteau, spoke of the possibility of 5______ the seabed. He said that some permanent stations were to be set up under the sea, and some undersea farms would provide food for the growing population of the world.

some time ago scientists began experiments