Tag: Global Warming

Study: farmers could increase their production and contribute to reduce up to one gigaton of metric carbon emissions

No Comments

by  | Dec 5, 2017


A new study presented at the Bonn Climate Summit, COP23 – produced by an international group of scientists led by the Chinese Academy of Sciences, The Nature Conservancy (TNC) and the Center for Tropical Agricultural Research (CIAT), and published in Scientific Reports – has revealed how agricultural production could contribute significantly in the fight against climate change, a matter of utmost importance that will continue in discussions towards COP24.

Scientists have already established that agricultural production depletes carbon from soils as a result of over-tillage (digging or removing soil) and chemical fertilizers, which is estimated to cause between 50 and 70 percent of the loss of water reserves. carbon in agricultural soils worldwide (Lal, 2004). Taking into account that agricultural soils are capable of sequestering carbon dioxide from the atmosphere when farmers use sustainable practices – such as increased use of manure, surface crops, vegetative cover, conservation tillage, fertilization management, as well as natural climate solutions, like agroforestry – the international group of scientists sought to establish in which regions of the world the highest carbon capture could be obtained through these activities.

Using a small increase of carbon in soils -experts consider that it is affordable in almost all arable soils- the scientists found that better management of soils for agriculture could contribute to an annual emission reduction of between 0.9 and 1.85 billion tons per year, equivalent to almost the total emissions of Brazil and Argentina, or the removal of between 215 and 400 million cars of circulation .

Justin Adams, TNC’s global executive director of Land, said that “natural climate solutions are essential to address climate change and investing in our soils is a strategy with enormous untapped potential-a potential that we could use if we began to think holistically about the type of actions and policies needed from the top down and from the ground up. If we want to satisfy the growing demand for food, maintaining global health and biodiversity, and abate climate change, then soils are our least valued ally. “

The study found that most of the carbon in the soil is stored in the northern hemisphere, with the countries of North America, Northern Europe, and Russia having the largest reserves of organic carbon in their arable land. In contrast, large tracts of arable land in India, the Sahel in Africa, Northern China, and Australia, are low in carbon.

Although the capacity to increase carbon in soils depends to a large extent on their typology and the environment, the main agricultural producing countries showed significant potential for carbon capture.

“Agricultural production in Latin America is fundamental for its economy. In fact, the region is considered as the food basket of the planet, since most of its production is exported to countries outside the region, “said Ginya Truitt Nakata, director of Land for Latin America of the TNC. “Then we have an enormous potential in terms of a significant contribution to the global mitigation of the effects of climate change through carbon sequestration since most of their countries are important agricultural producers with large tracts of land. cultivable “.

Additionally, 7 Latin American countries are among the 40 countries with the highest presence of carbon in their arable land: Brazil, Colombia, Chile, Ecuador, Peru, Argentina, and Guatemala.

The scientists also highlighted other important benefits of sustainable soil management, including higher yields for better soil fertility and better water retention capacity, which also help farmers adapt better to climate change. In this sense, it is estimated that the degradation of soils in Latin America reaches around 70 percent, according to the UN, which implies that improving agricultural practices can be a public policy incentive to maximize the additional benefits provided by healthy soils.

Table 1. Countries with the greatest potential for carbon capture by agricultural production compared to cars out of circulation (high scenario):

Table 2. Analysis of Organic Carbon Available in Cultivable Soils for Latin America and the Caribbean (most representative / high scenario):

“Soils are the basis of all food production. Healthier soils store more carbon and produce more food. Investing in better soil management will make our farming systems more productive and resilient to future impacts and stresses. “

Louis Verchot

Director of the Research Area in Soils and Landscapes for Sustainability (SoiLS) of CIAT. , International Center for Tropical Agriculture

 

The full study in English is available at www.nature.com/articles/s41598-017-15794-8 .

To access the data and maps, visit: http://ciat.cgiar.org/global-soil-carbon

 

Funding for this study was granted by the International Center for Tropical Agriculture (CIAT) and the CGIAR Research Program on Water, Land, and Ecosystems (WLE), with additional support from The Nature Conservancy (TNC) , and the Center of Studies of Mountain Ecosystems (CMES), the Kunming Institute of Botany and the Key Program of Investigation of Border Sciences of the Chinese Academy of Sciences.


Article Disclaimer: This article was published by the CIAT and retrieved on 12/07/2017 and posted here for information and educational purposes only. The views and contents of the article remain those of the authors. We will not be held accountable for the reliability and accuracy of the materials. If you need additional information on the published contents and materials, please contact the original authors and publisher. Please cite the authors, original source, and INDESEEM Inc. accordingly.


 

New study: Up to 7 billion tonnes of Carbon Dioxide can be removed from the atmosphere each year through better soil management on farm land

No Comments

by  | Nov 14, 2017


By better managing farmland soil, the amount of carbon stored in the top 30 centimeters of the soil could increase an extra 0.9 to 1.85 gigatons each year, say authors of a new study published today in Scientific Reports.

This is equivalent to carbon globally emitted by the transport sector (1.87 gigatons of Carbon); and equivalent to 3 – 7 billion tonnes of CO2 which could be removed from the atmosphere. For comparison, the US emits 5 billion tonnes of CO2 equivalent each year (Edgar database, 2015).

The maps in the new study show how much carbon could be stored per hectare each year, which will be vital for designing global mitigation strategies, for achieving targets set out in the Paris Climate Agreement.

Since the industrial revolution, 50-70 percent of the carbon stored in the soil has been lost to the atmosphere, contributing to harmful greenhouse gas emissions in the form of carbon dioxide. Since farmland is already intensively managed, improving the way it is managed is a practical step to reduce carbon in the atmosphere, say authors.

Soil organic carbon (SOC) in the top 30 cm, currently (T0), on all available cropland soils globally (i.e. those not excluded from the analysis as high SOC soils or sandy soils). Maps were produced based upon a geospatial analysis of datasets from the SoilsGrids250 database19, using ESRI ArcGIS software (version 10.3; www.esri.com).

Soil organic carbon (SOC) in the top 30 cm, currently (T0), on all available cropland soils globally (i.e. those not excluded from the analysis as high SOC soils or sandy soils). Maps were produced based on a geospatial analysis of datasets from the SoilsGrids250 database 19, using ESRI ArcGIS software (version 10.3; www.esri.com).

Dr. Robert Zomer, from the Kunming Institute of Botany, Chinese Academy of Sciences and lead author of the study, said: “Our findings show that turning soils into carbon sinks can sequester significant amounts of carbon in cropland soils. Our research shows soils can be part of the solution to combat climate change – and by doing so we can improve soil health.

The findings illustrate that most of the world’s carbon is stored in cooler, wetter, parts of the world in the northern hemisphere; and less in the tropics where it is hotter or drier. North America, Russia, and Europe currently store for over half of the world’s carbon in croplands.

The United States showed the highest total annual potential to store carbon in the soil, followed by India, China, Russian and Australia, if management is improved. The improved practices, among others, include, using compost or (green) manure, mulching, zero tillage, cover cropping, and other regenerative and natural climate solutions, such as agroforestry.

The annual increase in soil organic carbon (SOC) in the top 30 cm, on all available cropland soils globally (i.e. those not excluded from the analysis as high SOC or sandy soils) under the medium scenario (i.e. an increase in percent SOC of 0.27 over 20 years). Maps were produced based on a geospatial analysis of datasets from the SoilsGrids250 database19, using ESRI ArcGIS software (version 10.3; www.esri.com).

“Regenerating soil organic carbon is a foundational strategy for conservation, through which we can provide food and water sustainably and help tackle climate change.  Analyses like this help us understand the importance of soil management for reaching climate goals. The question now is: how can we unlock this potential?” asked Dr. Deborah Bossio, Lead Soil Scientist at The Nature Conservancy.

Tropical soils are especially sensitive to management, as they lose carbon faster than their counterparts in temperate regions, due to higher temperatures and rainfalls. Dr. Rolf Sommer, CIAT’s principle soil scientist and part of the CGIAR Research Program on Water, Land, and Ecosystems, which funded the study said:

“In western Kenya, over half of all carbon stored in the soil has been released to the atmosphere in the last 30-100 years. That’s roughly twice the speed we would see in other parts of the world like in parts of Europe.”

The authors point out that further research is needed to pinpoint which soil management practices are possible in specific areas to sequester more carbon. Especially in developing countries like Ethiopia, where carbon sequestration in soils could significantly reduce emissions and make agriculture carbon neutral, farmers are often very resource constrained, with few options to actively manage soils.

Soils are the basis of all food production. Healthier soils store more carbon and produce more food. Investing in better soil management will make our agricultural systems more productive and resilient to future shocks and stresses.

Dr. Louis Verchot

Co-author and Director of the Soil Research Area, International Center for Tropical Agriculture

Although there is vast potential, turning soils into a carbon sink requires climate-smart solutions and supportive policy enabling environments, to catalyze a change in countries outlined in the study.

Full citation: Zomer, Robert J.; Bossio, Deborah A.; Sommer, Rolf; Verchot, Louis V.. 2017. Global Sequestration Potential of Increased Organic Carbon in Cropland Soils. Scientific Reports . 7: 15554.

“Global Sequestration Potential of Increased Organic Carbon in Cropland Soils” was published in the online journal Scientific Reports on 14th November 2017.


Article Disclaimer: This article was published by the CIAT and retrieved on 11/24/2017 and posted here for information and educational purposes only. The views and contents of the article remain those of the authors. We will not be held accountable for the reliability and accuracy of the materials. If you need additional information on the published contents and materials, please contact the original authors and publisher. Please cite the authors, original source, and INDESEEM accordingly.


 

 

 

Summer sea ice melt in the Arctic

No Comments
170724133153_1_540x360

A large circular sea ice floe covered with melt ponds and surrounded by smaller floes, as seen from an Operation IceBridge flight on July 17, 2017. Credit: NASA/Nathan Kurtz


Date: July 24, 2017, Source: NASA/Goddard Space Flight Center


Summary: Earlier this year Arctic sea ice sank to a record low wintertime extent for the third straight year. Now NASA is flying a set of instruments north of Greenland to observe the impact of the melt season on the Arctic’s oldest and thickest sea ice.

Earlier this year Arctic sea ice sank to a record low wintertime extent for the third straight year. Now NASA is flying a set of instruments north of Greenland to observe the impact of the melt season on the Arctic’s oldest and thickest sea ice.

Operation IceBridge, NASA’s airborne survey of polar ice, launched a short campaign on July 17 from Thule Air Base, in northwest Greenland. Weather permitting, the IceBridge scientists are expecting to complete six, 4-hour-long flights focusing on sea ice that has survived at least one summer. This older multi-year ice, once the bulwark of the Arctic sea ice pack, has dramatically thinned and shrunk in extent along with the warming climate: in the mid-1980s, multi-year ice accounted for 70 percent of total winter Arctic sea ice extent; by the end of 2012, this percentage had dropped to less than 20 percent.

“Most of the central Arctic Ocean used to be covered with thick multi-year ice that would not completely melt during the summer and reflect back sunshine,” said Nathan Kurtz, IceBridge’s project scientist and a sea ice researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But we have now lost most of this old ice and exposed the open ocean below, which absorbs most of the sun’s energy. That’s one reason the Arctic warming has increased nearly twice the global average — when we lose the reflecting cover of the Arctic Ocean, we lose a mechanism to cool the planet.”

The sea ice flights will survey melt ponds, the pools of melt water on the ice surface that may contribute to the accelerated retreat of sea ice. Last summer, IceBridge carried a short campaign from Barrow, Alaska, to study young sea ice, which tends to be thinner and flatter than multi-year ice and thus has shallower melt ponds on its surface.

“The ice we’re flying over this summer is much more deformed, with a much rougher topography, so the melt ponds that form on it are quite different,” Kurtz said.

IceBridge is also flying a set of tracks to locate areas of sea ice that the mission already flew over in March and April, during its regular springtime campaign, to measure how the ice has melted since then.

“The sea ice can easily have drifted hundreds of miles between the spring and now, so we’re tracking the ice as it’s moving from satellite data,” Kurtz said.

The summer research flights are aboard an HU-25C Guardian Falcon aircraft from NASA’s Langley Research Center in Hampton, Virginia. The plane is carrying a laser instrument that measures changes in ice elevation and a high-resolution camera system to map land ice, as well as two experimental instruments.

IceBridge’s main instrument, the Airborne Topographic Mapper laser altimeter, was recently upgraded to transmit 10,000 pulses every second, over three times more than the previous laser versions and with a shorter pulse than previous generations. The upgrade will allow the mission to measure ice elevation more precisely as well as try out new uses on land ice. During this campaign, IceBridge researchers want to experiment whether the laser is able to measure the depth of the aquamarine lakes of melt water that form on the surface of the Greenland Ice Sheet in the summer. Large meltwater lakes are visible from space, but depth estimates from satellite imagery — and thus the volume of water they contain — have large uncertainties. Those depth estimates are key to calculating how much ice melts on Greenland’s ice sheet surface during the summer.

“Scientists have measured the depth of these lakes directly by collecting data from Zodiacs,” said Michael Studinger, principal investigator for the laser instrument team. “It’s very dangerous to do this because these lakes can drain without warning and you don’t want to be on a lake collecting data when that happens. Collecting data from an airborne platform is safer and more efficient.”

Researchers have used lasers to map the bottom of the sea in coastal areas, so Studinger is optimistic that the instrument will be able to see the bottom of the meltwater lakes and that possibly IceBridge will expand this new capability in the future. A mission that IceBridge flew on July 19 over a dozen supraglacial lakes in northwest Greenland gathered a set of measurements that Studinger’s team will analyze over the following weeks and months.

 


Story Source:

Materials provided by NASA/Goddard Space Flight CenterNote: Content may be edited for style and length.


Cite This Page:

NASA/Goddard Space Flight Center. “Summer sea ice melt in the Arctic.” ScienceDaily. ScienceDaily, 24 July 2017. <www.sciencedaily.com/releases/2017/07/170724133153.htm>.


Article Disclaimer: This article was published by the Science Daily and retrieved on 07/28/2017 and posted here for information and educational purposes only. The views and contents of the article remain those of the authors. We will not be held accountable for the reliability and accuracy of the materials. If you need additional information on the published contents and materials, please contact the original authors and publisher. Please cite the authors, original source, and INDESEEM accordingly.


 

 

 

South Asia’s climate hazard hotspots

No Comments
Before-disaster-strikes

Photo: V. Dakshinamurthy / IWMI


Mapping risks and estimating impacts on people and agriculture

Extreme climate events are taking a heavy toll in countries around the world, destroying lives and livelihoods. Since the late 1980s, the frequency of such disasters has increased – from an average of 195 per year during 1987-1998 to 338 per year during 2000-2011, according to researchers at the Centre for Research on the Epidemiology of Disasters (CRED) in Belgium.

In response, governments are giving high priority to disaster risk reduction, alongside their efforts to mitigate climate change by curbing greenhouse gas emissions. To reduce risks effectively and equitably, however, they urgently need quantitative methods to assess the vulnerability of specific populations to multiple climate-related hazards. Such methods will provide national disaster management organizations with a stronger basis on which to target risk reduction aid and allocate finance for climate adaptation in line with climate justice principles.

Beyond global snapshots

Mapping Multiple Climate-related Hazards in South Asia

The International Water Management Institute (IWMI) has just given a boost to such efforts with a new research report titled Mapping Multiple Climate-related Hazards in South Asia. The study was launched recently at a policy dialogue organized by IWMI jointly with the Government of Bihar, India; the Indian Council of Agricultural Research (ICAR); Japan’s Ministry of Agriculture, Forestry and Fisheries; and two CGIAR Research Programs – Water, Land and Ecosystems (WLE), which IWMI leads, and Climate Change, Agriculture and Food Security (CCAFS)

Bihar is the country’s most flood-prone state, having suffered agricultural losses with an estimated value of US$340 million over the past 12 years. It is the logical testing ground for index-based flood insurance under a project being carried out with the aforementioned CGIAR Research Programs.

“Countries in the region must coordinate actions to cope with adverse climate impacts, such as seasonal floods, drought, landslides, cyclones and sea-level rise,” says Giriraj Amarnath, lead author of the IWMI report and leader of the Institute´s Water Risks research group. At a global level, the World Bank and other organizations have conducted large-scale analysis of natural disasters, making it possible to pinpoint hotspots. But according to Amarnath, the resulting “global snapshots” are not detailed enough to guide local risk reduction efforts.

In South Asia, the assessment of multiple risks has increased over the last decade, though most studies are confined to the state or district level. In contrast, the IWMI study closes major knowledge gaps by offering a detailed approach to map climate hazards and identify areas at risk on a regional and sub-national scale.

Vulnerable people and places

Relying on the vulnerability assessment framework of the Intergovernmental Panel on Climate Change (IPCC), the IWMI study uses a combined index (based on hazard, exposure and adaptive capacity) to identify areas that are susceptible to extreme risk. For this purpose, researchers used data on the spatial distribution of climate-related hazards in 1,398 districts of Bangladesh, Bhutan, India, Nepal, Pakistan and Sri Lanka.

FIGURE 4. Spatial distribution of drought frequency based on 13 years’ time series of MODIS imagery.

Based on its analysis of risk exposure in these countries, the study shows that approximately 750 million people – over 45 percent of the region´s entire population – were affected by climate hazards during the decade after 2000. Of this total, 72 percent were in India, 12 percent each in Bangladesh and Pakistan, and the remaining 4 percent in Bhutan, Nepal, and Sri Lanka.

Study results emphasize that agriculture is particularly vulnerable to climate extremes (mostly drought and flooding), with more than 58 percent of agricultural areas across the region damaged by multiple hazards. Drought affects the largest area (786,000 square kilometers), followed by extreme temperature, extreme rainfall, floods and sea-level rise.

The IWMI study includes an overall climate change vulnerability map, which makes it easy to visualize and identify climate-hazard hotspots. The results offer few surprises, confirming the common perception that the most vulnerable parts of South Asia are Bangladesh´s coastal region; the Indian states of West Bengal, Orissa, Andhra Pradesh and Gujarat; and Sindh in Pakistan. This is a result of their exposure to sea-level rise and position in the transboundary basins of the Ganges, Brahmaputra and Meghna Rivers, which are prone to annual flooding.

FIGURE 21. Climate change vulnerability map of South Asia based on exposure, sensitivity and adaptive capacity to multiple hazards.

From awareness to action

There is growing awareness of the need to prepare for and respond to the impacts of climate change. Finding better solutions to manage disaster risk is crucial for compliance with the Sustainable Development Goals, Sendai Framework for Disaster Risk Reduction and Paris Climate Change Agreement. The methodology that IWMI presents in its new report is a step in the right direction and has potential for application to other regions.

“But much remains to be done toward generating more data on the ground at a finer scale,” says Amarnath. “And this, in turn, requires better coordination among various sectors to develop comprehensive risk assessments that can inform disaster risk management plans and risk-financing strategies.”


Read the report

Amarnath, Giriraj; Alahacoon, Niranga; Smakhtin, V.; Aggarwal, P. 2017. Mapping multiple climate-related hazards in South Asia. Colombo, Sri Lanka: International Water Management Institute (IWMI) 41p. (IWMI Research Report 170)[DOI] | Fulltext (6.07 MB)


 


Article Disclaimer: This article was published by the International Water Management Institute and retrieved on 07/28/2017 and posted here for information and educational purposes only. The views and contents of the article remain those of the authors. We will not be held accountable for the reliability and accuracy of the materials. If you need additional information on the published contents and materials, please contact the original authors and publisher. Please cite the authors, original source, and INDESEEM accordingly.


 

Agricultural scientists urge new global crop alliance to secure future food supply

No Comments
24520671422_a45ac55a90_b-672x448

Farmer Gashu Lema’s son harvests improved variety “Kubsa” wheat


EL BATAN, Mexico (CIMMYT) – At a time when weather patterns are becoming less predictable and population pressures on food supply are increasing, a group of crop scientists are laying the groundwork for an international crop network to systematically tackle threats to global food security.

Research focused on specific crops achieves progressive genetic gains, but scientists need to adopt a more internationally oriented and integrated approach to leverage technology, expertise and infrastructure with greater efficiency and purpose, said Matthew Reynolds, a distinguished scientist and wheat breeder at the International Maize and Wheat Improvement Center (CIMMYT) in an opinion piece published this week in the journal Science.

Already 795 million poor people do not get enough food to eat, according to the U.N. Food and Agriculture Organization (FAO). By 2030, the number of people living in poverty could increase between 35 and 122 million in large measure because of the impact of climate change on the agricultural sector, the FAO reports.

“We understand how to make crops more resilient to heat and drought, but we’re at a point where we need to accelerate our work.” said Reynolds, backed by a team of co-authors from the scientific community. “Since these problems are transnational in nature, a more global network could accelerate our efforts while increasing efficiency and helping to avoid duplication.”

Scientists plan to deploy the new Global Crop Improvement Network (GCIN) to take comparative approaches across all major crops and environments to enhance such traits as root access to water using remote sensing, which often requires costly mobile, airborne or satellite technology.

Through successful wheat-specific collaboration, since the early 1960s, the International Wheat Improvement Network (IWIN), part of the CGIAR-affiliated group of agricultural researchers, has made economically efficient and environmentally sound impacts in crop improvement, which serve as a template for the projected success of GCIN.

Scientists within IWIN undertake breeding efforts aimed at 12 different wheat mega-environments, testing new wheat genotypes at 700 field sites in more than 90 countries. Each year they produce some 1,000 high-yielding, disease-resistant wheat lines, which are delivered as international public goods.

A recent study on wheat improvement shows that CGIAR varieties cover about half of the world’s wheat growing area, through IWIN, delivering an economic punch of from $2.2 billion to more than $3 billion a year for resource-poor farmers and consumers.

“The benefit cost ratio of the investment is 100 to 1, even without taking into account the avoided cost of disease pandemics and the land saved from cultivation due to increased yields; economic analysis indicate at least 20 million hectares of natural ecosystem have been spared the plough,” Reynolds said.

“High transaction costs and instability of crop funding have hamstrung urgently needed research,” he added. “This is senseless in light of the extraordinary return on investment to IWIN which could be transferred to GCIN.”

Through a crop-wide collaboration, international scientists can boost benefits from practical work with national agricultural research systems, improving the value of “in kind contributions,” he said.

Aims include standardizing data and phenotyping techniques to best practises, ensuring that information can be shared and understood worldwide.

This approach will also encourage upstream researchers to venture from working exclusively in controlled facilities to realistic field environments, bringing cutting edge technologies with them, Reynolds said.

Data sharing could lead to more accurate descriptions of environments and experimental treatments. Currently, data is often only available selectively and a network would promote it through open access programs.

The benefits of integrated research through the CGIAR group of agricultural researchers and the FAO are well established, but the network under discussion could enhance and improve information sharing transnationally.

Experimental fields – or field laboratories – which are essential for translating scientific breakthroughs to improved crop yields, could at times benefit from more strategic relocation. Often they are in certain areas due to historical, financial or political reasons, not because of current practical needs, Reynolds explained.

Climate change is expected to lead to overall warmer temperatures and increase the intensity of droughts, floods and storms, negatively affecting food security and livelihoods. Climate modelling indicates that sea levels will rise and patterns of flooding and drought will change due to glacial melt at high altitudes.

Higher temperatures will affect crop yields and erratic rainfall could affect both yields and quality. For poor people spending most of their income on food, related price hikes could make it much more difficult to cope.

“A more globally oriented, problem-solving research effort will increase the efficiency of global investment in agriculture and help ensure food security,” Reynolds said, adding that public-private partnerships could be harnessed to drive globally coordinated research.


Article Disclaimer: This article was published by the CGIAR and retrieved on 07/28/2017 and posted here for information and educational purposes only. The views and contents of the article remain those of the authors. We will not be held accountable for the reliability and accuracy of the materials. If you need additional information on the published contents and materials, please contact the original authors and publisher. Please cite the authors, original source, and INDESEEM accordingly.


 

Climate models underestimate global warming by exaggerating cloud brightening

No Comments
160407221445_1_540x360

Credit: Photo courtesy of NASA


Date:April 7, 2016Source:DOE/Lawrence Livermore National Laboratory

Summary: Researchers have found that climate models are aggressively making clouds ‘brighter’ as the planet warms. This may be causing models to underestimate how much global warming will occur due to increasing carbon dioxide.


Many clouds surround the Southern Ocean. Lawrence Livermore scientists have found that climate models don’t accurately portray clouds and in turn underestimate global warming.

Researchers at Lawrence Livermore National Laboratory and Yale University have found that climate models are aggressively making clouds “brighter” as the planet warms. This may be causing models to underestimate how much global warming will occur due to increasing carbon dioxide. The research appears in the April 8 edition of Science.

As the atmosphere warms, clouds become increasingly composed of liquid rather than ice, making them brighter. Because liquid clouds reflect more sunlight back to space than ice clouds, this “cloud phase feedback” acts as a brake on global warming in climate models.

But most models’ clouds contain too much ice that is susceptible to becoming liquid with warming, which makes their stabilizing cloud phase feedback unrealistically strong. Using a state-of-the-art climate model, the researchers modified parameters to bring the relative amounts of liquid and ice in clouds into agreement with clouds observed in nature. Correcting the bias led to a weaker cloud phase feedback and greater warming in response to carbon dioxide.

“We found that the climate sensitivity increased from 4 degrees C in the default model to 5-5.3 degrees C in versions that were modified to bring liquid and ice amounts into closer agreement with observations,” said Yale researcher Ivy Tan, lead author of the paper.

Climate sensitivity refers to the change in global mean surface temperature due to a doubling of carbon dioxide. Climate models predict between 2.1 and 4.7 degrees C (3.75 to 8.5 degrees F) of warming in response to a doubling of carbon dioxide.

“We saw a systematic weakening of the cloud phase feedback and increase in climate sensitivity as we transitioned from model versions that readily convert liquid to ice below freezing to model versions that can maintain liquid down to colder temperatures, as observed in nature,” Tan explained.

In nature, clouds containing both ice crystals and liquid droplets are common at temperatures well below freezing. As the atmosphere warms due to carbon dioxide emissions, the relative amount of liquid in these so-called mixed phase clouds will increase. Since liquid clouds tend to reflect more sunlight back to space than ice clouds, this phase feedback acts to reduce global warming. The icier the clouds to begin with, the more liquid is gained as the planet warms; this stabilizing feedback is stronger in models containing less liquid relative to ice at sub-freezing temperatures.

“Most climate models are a little too eager to glaciate below freezing, so they are likely exaggerating the increase in cloud reflectivity as the atmosphere warms,” said LLNL coauthor Mark Zelinka. “This means they may be systematically underestimating how much warming will occur in response to carbon dioxide.”

These results add to a growing body of evidence that the stabilizing cloud feedback at mid- to high latitudes in climate models is overstated. Moreover, several recent studies have concluded that other important cloud feedbacks also are likely to exacerbate warming rather than dampen it. These include amplifying feedbacks from increases in cloud top altitude and from decreases in the coverage of subtropical low clouds.

“The evidence is piling up against an overall stabilizing cloud feedback,” concluded Zelinka. “Clouds do not seem to want to do us any favors when it comes to limiting global warming.”


Story Source:

Materials provided by DOE/Lawrence Livermore National LaboratoryNote: Content may be edited for style and length.


Journal Reference:

  1. I. Tan, T. Storelvmo, M. D. Zelinka. Observational constraints on mixed-phase clouds imply higher climate sensitivityScience, 2016; 352 (6282): 224 DOI: 10.1126/science.aad5300

Article Disclaimer: This article was published by the Science Daily and retrieved on 07/22/2017 and posted here for information and educational purposes only. The views and contents of the article remain those of the authors. We will not be held accountable for the reliability and accuracy of the materials. If you need additional information on the published contents and materials, please contact the original authors and publisher. Please cite the authors, original source, and INDESEEM accordingly.


 

 

%d bloggers like this: