Sentences with phrase «say atmospheric carbon»

Leading climate scientists say atmospheric carbon dioxide concentrations should be reduced to 350 parts per million to avoid catastrophic, irreversible impacts.

Doing that may have just gotten a lot tougher — a new study says atmospheric carbon dioxide levels haven't been this high in more than two million years.

Not exact matches

Darin Toohey, a professor at the University of Colorado's atmospheric and oceanic sciences department and one of the paper's authors, says black carbon absorbs shortwave radiation from the sun, causing the atmosphere to heat up.

At a Feb. 7 hearing of Juliana, et al v. United States of America, et al — a case a group of kids, young adults and environmentalists brought in 2015 against the U.S. government — Frank Volpe said he didn't know whether carbon dioxide levels had reached 400 parts per million, a measurement of atmospheric concentration.

«These studies are a wake - up call ahead of U.N. Climate Week — we must not only zero out CO2 emissions by 2050, but also rapidly limit superpollutants like HFCs and methane, and even undertake atmospheric carbon removal,» said Bledsoe, a former Clinton White House climate adviser.

Worldwide, carbon storage has the capability to provide more than 15 percent of the emissions reductions needed to limit the rise in atmospheric CO2 to 450 parts per million by 2050, an oft - cited target associated with a roughly 50 - percent chance of keeping global warming below 2 degrees, but that would involve 3,200 projects sequestering some 150 gigatons of CO2, says Juho Lipponen, who heads the CCS unit of the International Energy Agency in Paris.

The team says these factors combined to cause a sudden drop in atmospheric carbon dioxide, which would have cooled the planet sufficiently to cause the ice age.

«Stabilizing or reducing atmospheric carbon dioxide concentrations, therefore, requires very deep reductions in future emissions to compensate for past emissions that are still circulating in the Earth system,» the draft report says.

An observed long - term increase in the number of these clouds may be due in part to the rise in atmospheric carbon dioxide levels, he says.

Jacobson, the director of Stanford's Atmosphere / Energy Program and a senior fellow at the Woods Institute for the Environment and the Precourt Institute for Energy, said almost 8.5 billion tons of atmospheric carbon dioxide — or about 18 percent of all anthropogenic carbon dioxide emissions - comes from biomass burning.

«I don't think many studies have realized this yet: Black carbon impacts global warming in at least four different ways,» said V. Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography.

James McCarthy, professor of biological oceanography at Harvard, says this summer's record heat and dryness could have occurred with lower atmospheric carbon dioxide concentrations — but it would have been highly unlikely.

There are signs, however, that the ocean's capacity to sequester atmospheric carbon dioxide has been decreasing over the past few decades, says climate scientist Samuel Jaccard of ETH Zurich in Switzerland.

Franck Montmessin of the LATMOS atmospheric research centre in France says ozone forms when sunlight breaks up carbon dioxide molecules on the planet's daylight side.

«The Paleocene - Eocene thermal maximum has stood out as a striking, but contested, example of how 21st - century - style atmospheric carbon dioxide buildup can affect climate, environments and ecosystems worldwide,» says Bowen, an associate professor of geology and geophysics at the University of Utah.

«If the initial atmospheric carbon dioxide concentration were half its actual value, we would currently be experiencing the climate expected for the year 2050,» says Archer, setting out one possible scenario.

The trouble is, ice cores are the gold standard for estimating past atmospheric carbon dioxide levels, and Marchant says the Dry Valley glaciers are the only ones known to contain ice that old.

«There is a danger in believing that land carbon sinks can solve the problem of atmospheric carbon emissions because this legitimises the ongoing use of fossil fuels,» Professor Mackey said.

«Wheat's photosynthetic pathway evolved 100 million years ago when atmospheric carbon dioxide levels were up to 10 times higher than they are today,» he said.

Although plants grown in high levels of carbon dioxide — say, double the current atmospheric concentrations — initially grow rapidly, the growth tapers off within weeks and the plants wind up with a low protein content.

David Fahey, an atmospheric scientist at the National Oceanic and Atmospheric Administration in Boulder, Colorado, said that the researchers will need to do additional analyses to reduce the «significant uncertainties associated with the role of black carbon in the climate.»

The authors said the study underlines the increasing vulnerability of calcified animals to ocean acidification, which occurs as the ocean absorbs more atmospheric carbon emitted through the burning of fossil fuels.

«The atmospheric carbon dioxide observations are important because they show the combined effect of ecological changes over large regions,» says Graven.

«With atmospheric carbon dioxide at unprecedented levels, our sense of urgency has only increased,» said Basilio.

«We found that the Antarctic microbes have evolved mechanisms to live on air instead, and they can get most of the energy and carbon they need by scavenging trace atmospheric gases, including hydrogen and carbon monoxide,» she says.

As for the paper's conclusion that removing atmospheric carbon is necessary in order to achieve the 2 ˚C target, climate scientist Richard Moss of the Pacific Northwest National Laboratory's Joint Global Change Research Institute in College Park, Maryland, says that's a nearly impossible goal «with what we know about today.»

Dr Tina Van De Flierdt, co-author from the Department of Earth Science and Engineering at Imperial College London, says: «The Pliocene Epoch had temperatures that were two or three degrees higher than today and similar atmospheric carbon dioxide levels to today.

«Changes in ocean conditions that affect fish stocks, such as temperature and oxygen concentration, are strongly related to atmospheric warming and carbon emissions,» said author Thomas Frölicher, principal investigator at the Nippon Foundation - Nereus Program and senior scientist at ETH Zürich.

The north Atlantic Ocean is globally important, as it is a sink for atmospheric carbon dioxide, said Eric Achterberg, chief scientist for the research cruise and lead author of the study.

«A limit to the availability of iron in this region means that the ocean is less efficient in its uptake of atmospheric carbon dioxide,» he said.

Tests from one to 50 atmospheric pressures showed the Rice compound captured a fifth of its weight in carbon dioxide but no measurable amount of methane, Barron said, and the material did not degrade over many absorption / desorption cycles.

Oxford University atmospheric physicist Raymond Pierrehumbert, who is among the scientists who believe cutting methane should be less of a priority than cutting carbon dioxide to tackle climate change, said the study is useful in evaluating methane capture systems at landfills.

«Now with treaties banning atmospheric testing, carbon - 14 levels are tapering off,» he says.

For example, he said, most participants recognized that carbon dioxide increases global temperatures, yet mistakenly indicated that rising levels of atmospheric CO2 are expected to «reduce photosynthesis in plants.»

«We grew teosinte in the conditions that it encountered 10,000 years ago during the early Holocene period: temperatures 2 - 3 degrees Celsius cooler than today's with atmospheric carbon dioxide levels at around 260 parts per million,» said Dolores Piperno, senior scientist and curator of archaeobotany and South American archaeology at the Smithsonian's National Museum of Natural History and the Smithsonian Tropical Research Institute, who led the project.

April will be the first time in human history where levels of atmospheric carbon dioxide were higher than 400 parts per million for an entire month, one scientist who monitors the levels said.

Armed with this information, scientists will be able to do a much better job forecasting atmospheric carbon dioxide concentrations in the future, he said, and in understanding the role of human activities on the carbon cycle.

«The potential for biochar to permanently sequester atmospheric carbon is on the order of a billion tons per year, if sustainable practices are used,» said Amonette.

«Controlling black carbon may be the only way of preventing the loss of the Arctic completely,» said Mark Jacobson, an atmospheric scientist who researches air pollution and climate change at Stanford University.

Using our carbon cycle model we calculate that if we extract 100 ppm of CO2 from the air over the period 2030 — 2100 (10/7 ppm per year), say storing that CO2 in carbonate bricks, the atmospheric CO2 amount in 2100 will be reduced 52 ppm to 358 ppm, i.e., the reduction of airborne CO2 is about half of the amount extracted from the air and stored.

Raymond Pierrehumbert, an Oxford University atmospheric physics professor who believes cutting carbon dioxide emissions is more urgent than cutting methane emissions, said Howarth's research offers little new information about the role of natural gas production in global warming.

This is not particularly surprising, since it is expected that the importance of the new simulations will be seen in the differences between model types (i.e. including carbon cycles, atmospheric chemistry etc.), or in new kinds of diagnostics from say, the initialized decadal predictions, that weren't available before.

As if the title weren't misleading enough, the article goes on to say that «Many scientists believe the burning of fossil fuels is causing an increase in atmospheric carbon dioxide, triggering... the greenhouse effect.»

He and eight co-authors have drafted a fresh paper arguing that the world has already shot past a safe eventual atmospheric concentration of carbon dioxide, which they say would be around 350 parts per million, a level passed 20 years ago.

Phasing out these subsidies over the next decade would achieve more than 30 percent of the cuts in carbon emissions necessary to keep rising atmospheric temperatures at no more than 2 degrees Celsius above pre-industrial levels, the IEA says.

At a June 2006 Symposium, Dr. Katey Walter said, «The rapid thaw of permafrost can release this carbon nearly instantaneously, raising atmospheric carbon concentrations.»

«Our findings show that if we do not want to melt Antarctica, we can't keep taking fossil fuel carbon out of the ground and just dumping it into the atmosphere as CO2, like we've been doing,» says one of the report's authors, Ken Caldeira, an atmospheric scientist at Stanford University's Carnegie Institution for Science, California.

«Since the pre-industrial era, we have increased atmospheric CO2 [or carbon dioxide] concentration by about 100 parts per million, so this is really a different dimension,» she said.

The question, said Julia Pongratz, a postdoctoral researcher at the Carnegie Institution's Department for Global Ecology at Stanford University, was whether this regrowth could have locked up enough carbon to make a difference in global atmospheric carbon dioxide.

That may mean that natural factors, such as changes in solar radiation, played a larger role in atmospheric carbon dioxide than reforestation during this time, Pongratz said.