Global Warming
"Top climate scientist James Hansen tells the story of his involvement in the science of and debate over global climate change. In doing so he outlines the overwhelming evidence that change is happening and why that makes him deeply worried about the future."
What is Global Warming aka Climate Change?
Global warming is the increase of the average temperature in the atmosphere and oceans over time due primarily to human influences. Since the late 19th century, scientists have monitored the fluctuations in temperature and studied global warming theories and trends to determine the causes and to assess the extent to which they are due to human activity. The greenhouse effect is largely caused by human-generated carbon dioxide (CO2) and, to some extent, by increases in solar activity. The term "global warming" is used to imply a human influence while "climate change" is most often used in association with changes in climate with no easily identifiable cause, such as the processes that produced the Ice Ages.
Current climate models (simulations) based on estimates of increasing CO2 and, to a lesser extent, by decreasing sulfate aerosols, predict that temperatures will increase by 1.4-5.8°C (2.5-10.4°F) between 1990-2100. This is a somewhat wide range; however, it is difficult to predict CO2 emissions because of the number of variables involved. Some climate studies have shown that, even in the absence of the CO2 emission variable, global climate will increase by 0.5°C (0.9°F) over the next one hundred years due to warming caused just by the ocean. In addition, models predict that sea levels will rise by about 10 cm over the next century.
Evidence of global warming includes decreased snowfall, rising sea levels and changes to weather trends. Precipitation levels, precipitation patterns, cloud cover, severe weather, and other elements will be impacted by the increase in greenhouse gas concentrations in the atmosphere. "Greenhouse gases" are so named because they trap radiant energy from the sun that would otherwise be radiated back into space.
The Kyoto Protocol was developed by the United Nations Framework Convention on Climate Change (UNFCCC) as an international agreement to reduce greenhouse gas emissions worldwide. The Protocol was entered into force in February 2005, and signed by countries committed to reducing CO2 emissions and 5 other greenhouse gases. They may also engage in emissions trading, or the purchase of credits from other countries that remain under the limits of greenhouse gas emissions. In this way, countries that may exceed the limits can still comply with the protocol. To date, 141 countries have ratified the agreement. Unfortunately, neither the United States nor Australia have been participating, which has generated speculation as to whether the Kyoto Protocol will successfully reduce greenhouse gases, even if completely implemented by all signed countries.
Global climate change has been studied on a large scale based on analyses of global temperature fluctuations over thousands of years; for example, since the last Ice Age, which occurred approximately 12,000 years ago, global temperatures have been relatively stable. Studies on a smaller scale, however, show that temperatures in the lower troposphere have increased between 0.08 and 0.22°C per decade since 1979. Still, these modern day changes are not always linear, which has created a source of debate within the scientific community and the news media.
The study of paleoclimatology (ancient climates) is increasingly linked to modern day climate study. For example, the Earth was in an ice age for the last 160,000 years prior to the end of the last Ice Age. Earlier studies of this time period showed little variability in temperatures; however, more recent studies showed the variability to be about twice as great as previously published, indicating that temperature fluctuations are more frequent throughout time than first thought. However, this does not negate the impact of human activity on the current rate of global warming.
Climate change is caused by both natural and external forces, the latter including both human—greenhouse gases—and non-human causes such as changes in the Earth's orbit around the Sun, solar activity, and volcanic emissions. Science is increasingly pointing to human activities as the reason that global warming is accelerating.
The greenhouse gas theory started in the 19th century when the Swedish chemist and 1903 Nobel Laureate, Svante Arrhenius, determined that increases in greenhouse gas concentration would lead to higher global mean temperatures, while decreases would lead to colder global mean temperatures. His finding was a result of his research on ice ages, and was largely rejected by his peers at the time. A colleague of Arrhenius, Arvid Högbom, was one of the first scientists to study the carbon cycle. Arrhenius used his data to base his assessment that in 1890, emission and absorption of CO2 in the atmosphere were roughly in balance, and that burning fossil fuels would not cause problems. However, this was based solely on the use of coal, not on the use of fossil fuels in the automobile and other industries.
Opponents to the global warming theory postulate that water vapor and clouds will cancel out warming effect of CO2 emissions. However, the warming trends over the past few decades are increasingly negating the cancellation hypothesis. Furthermore, sophisticated computer models of the climate, validated by the scientific community in demonstrating accurate simulations of known climate variations such as El Niño events, have predicted that adding CO2 to the atmosphere will create a warmer climate in the future. The degree to which this warming will occur varies by model, however, and opponents of the global warming theory point out variables that models are not equipped to factor, such as changes in vegetation and cloud cover.
In spite of the dying debate, it is known that coal-burning power plants, automobile exhausts, factory smokestacks, and other waste vents contribute about 22 billion tons of CO2 (6 billion tons of pure carbon) and other greenhouse gases into the earth's atmosphere each year. CO2 levels have increased by about 31% since 1750, about 75% of which can be attributed to fossil fuel burning. The remaining 25% is largely due to land-use change, particularly deforestation.
In their 2006 report, the IPCC stated that the atmospheric concentration of CO2 has exceeded levels over the natural range for the last 650,000 years. The consensus is that human activity is, in almost all aspects of global warming, the most likely cause. This is a change from the previous report that stated human activity was merely a likely cause.
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Global Warming News :: ScienceDailyScientists core into California's Clear Lake to explore past climate change
One of the oldest lakes in the world, Clear Lake in northern California has deep sediments that contain a record of the climate and local plants and animals going back perhaps 500,000 years. Scientists are drilling cores from the sediments to explore 130,000 years of this history and fine-tune models for predicting the fate of today's flora and fauna in the face of global warming and pressure from a growing human population.
Stalagmite research suggests Earth has two modes of responding to change
By analyzing stalagmites, a team of researchers has determined that the climate signature in the tropics through four glacial cycles looks different in some ways and similar in others when compared to the climate signature at high latitudes. The results suggest that Earth's climate system might have two modes of responding to significant changes.
Increasing speed of Greenland glaciers gives new insight for rising sea level
Changes in the speed that ice travels in more than 200 outlet glaciers indicates that Greenland's contribution to rising sea level in the 21st century might be significantly less than the upper limits some scientists thought possible, a new study shows.
Ecosystem effects of biodiversity loss rival climate change and pollution
Loss of biodiversity appears to affect ecosystems as much as climate change, pollution and other major forms of environmental stress, according to results of a new study.
Decades of data show spring advancing faster than experiments suggest
Plants are leafing out and flowering sooner each year than predicted by results from controlled environmental warming experiments, according to data from a major new archive of historical observations.
Handful of heavyweight trees per acre are forest champs
Big trees three or more feet in diameter accounted for nearly half the biomass measured at a Yosemite National Park site, yet represented only one percent of the trees growing there, according to the largest quantitative study yet of the importance of big trees in temperate forests.
Experiments underestimate plant responses to climate change
Experiments may dramatically underestimate how plants will respond to climate change in the future. That's the conclusion of an analysis of 50 plant studies on four continents.
Ecosystem effects of biodiversity loss could rival impacts of climate change, pollution
Loss of biodiversity appears to impact ecosystems as much as climate change, pollution and other major forms of environmental stress, according to a new study. There has been growing concern that the very high rates of modern extinctions -- due to habitat loss, overharvesting and other human-caused environmental changes -- could reduce nature's ability to provide goods and services like food, clean water and a stable climate.
Stream temperatures don't parallel warming climate trend
A new analysis of streams in the western United States with long-term monitoring programs has found that despite a general increase in air temperatures over the past several decades, streams are not necessarily warming at the same rate.
Arctic sea-ice loss didn't happen by chance
The ongoing rapid retreat of Arctic sea ice is often interpreted as the canary in the mine for anthropogenic climate change. In a new study, scientists have now systematically examined the validity of this claim. They find that neither natural fluctuations nor self-acceleration can explain the observed Arctic sea-ice retreat. Instead, the recent evolution of Arctic sea ice shows a strong, physically plausible correlation with the increasing greenhouse gas concentration. For Antarctic sea ice, no such link is found – for a good reason.
Dry heat increases bark beetle bite
Climate change puts spruce forests at greater risk of bark beetle attacks.
Global warming: New research blames economic growth
It's a message no one wants to hear: to slow down global warming, we'll either have to put the brakes on economic growth or transform the way the world's economies work. That's the implication of an innovative study examining the evolution of atmospheric CO2, the most likely cause of climate change.
Night-warming effect found over large wind farms in Texas
Large wind farms in certain areas in the United States appear to affect local land surface temperatures, according to a new article.
Global warming refuge discovered near at-risk Pacific island nation of Kiribati
Scientists predict ocean temperatures will rise in the equatorial Pacific by the end of the century, wreaking havoc on coral reef ecosystems. But a new study shows that climate change could cause ocean currents to operate in a way that mitigates warming near a handful of islands right on the equator.
Pacific islands on equator may become refuge for corals in a warming climate due to changes in ocean currents
Scientists have predicted that ocean temperatures will rise in the equatorial Pacific by the end of the century, wreaking havoc on coral reef ecosystems. But a new study shows that climate change could cause ocean currents to operate in a surprising way and mitigate the warming near a handful of islands right on the equator. As a result these Pacific islands may become isolated refuges for corals and fish.
'Warming hole' delayed climate change over eastern United States
Climate scientists have discovered that particulate pollution in the late 20th century created a "warming hole" over the eastern United States -- that is, a cold patch where the effects of global warming were temporarily obscured. The findings have implications for industrial nations (like China) that have not yet tightened air quality regulations.
Oil palm surging source of greenhouse gas emissions
Continued expansion of industrial-scale oil palm plantations on the island of Borneo will become a leading cause of greenhouse gas emissions by 2020 unless strong forest and peatland protections are enacted and enforced, according to a new study.
Warm ocean currents cause majority of ice loss from Antarctica
Warm ocean currents are the dominant cause of recent ice loss from Antarctica, new research shows. New techniques have been used to differentiate, for the first time, between the two known causes of melting ice shelves - warm ocean currents attacking the underside, and warm air melting from above. This finding brings scientists a step closer to providing reliable projections of future sea-level rise.
Do urban 'heat islands' hint at trees of future?
A new study shows that common native red oak seedlings grow as much as eight times faster in New York's Central Park than in more rural, cooler settings in the Hudson Valley and Catskill Mountains. Red oaks and their close relatives dominate areas ranging from northern Virginia to southern New England, so the study may have implications for changing climate and forest composition over a wide region.
Study finds surprising Arctic methane emission source
The fragile and rapidly changing Arctic region is home to large reservoirs of methane, a potent greenhouse gas. As Earth's climate warms, the methane, frozen in reservoirs stored in Arctic tundra soils or marine sediments, is vulnerable to being released into the atmosphere, where it can add to global warming. Now a multi-institutional study has uncovered a surprising and potentially important new source of Arctic methane: the ocean itself.
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