NW Climate Science Digest

Aquatic Resources, Stream Flow, Hydrology in the Western U.S.

Study Demonstrates Shift from Snow to Rain Leads to Decrease in Streamflow

 In a warming climate, precipitation is less likely to occur as snowfall. A shift from a snow- towards a rain-dominated regime is currently assumed not to influence the mean streamflow significantly. The study argues however that mean streamflow is likely to be reduced for catchments that experience significant reductions in the fraction of precipitation falling as snow. With more than one-sixth of the Earth's population depending on meltwater for their water supply, and ecosystems that can be sensitive to streamflow alterations, the socio-economic consequences of a reduction in streamflow can be substantial. The study demonstrates that a higher fraction of precipitation falling as snow is associated with higher mean streamflow, compared to catchments with marginal or no snowfall. 

Identifying & protecting climate refuge lakes for coldwater fishes

The climate is changing and fish populations are changing in response (blogs 32, 34, 35, 42). Managing and conserving efficiently this century means having a good sense of where it’s all headed and committing limited conservation resources accordingly. Committing to the wrong places risks being run over by the climate change train or squandering resources on populations that would have been fine regardless of what the climate does (blog #52). The sweet spot lies between the two extremes and figuring out where our investments will tip the balance toward more desirable outcomes later this century. So as alluded in the previous blog (#56), this time we’re highlighting a set of related studies that constitute the current global gold standard in terms of developing the science, information, and management policies for making those commitments for one species in one landscape…

Climate warming contributes to native and invasive trout hybridization

Nature Clim. Change, 2014/07/, Vol 4, Issue 7, pp 620- 624, http://dx.doi.org/10.1038/nclimate2252

Results from a study conducted by Dr. Clint Muhlfeld, US Geological Survey, with funding support from the Great Northern LCC, was recently published in the journal Nature Climate Change. The paper reports that rapid climate warming contributes to hybridization between native and invasive trout species. Muhlfeld and his collaborators examined long-term genetic monitoring data with high-resolution climate and stream temperature predictions. Their findings indicate that invasive hybridization could result in genomic extinction for many native species. 

Extent of the rain-snow transition zone in the western U.S. under historic and projected climate

Klos, P. Z., T. E. Link, and J. T. Abatzoglou (2014), Extent of the rain-snow transition zone in the western U.S. under historic and projected climate, Geophys. Res. Lett., 41, doi:10.1002/2014GL060500

This study investigates the extent of the rain-snow transition zone across the complex terrain of the western United States for both late 20th century climate and projected changes in climate by the mid-21st century. Observed and projected temperature and precipitation data at 4 km resolution were used with an empirical probabilistic precipitation phase model to estimate and map the likelihood of snow versus rain occurrence. This approach identifies areas most likely to undergo precipitation phase change over the next half century. At broad scales, these projections indicate an average 30% decrease in areal extent of winter wet-day temperatures conducive to snowfall over the western United States. At higher resolution scales, this approach identifies existing and potential experimental sites best suited for research investigating the mechanisms linking precipitation phase change to a broad array of processes, such as shifts in rain-on-snow flood risk, timing of water resource availability, and ecosystem dynamics.

Next Steps for Managing Freshwater Resources in a Changing Climate

Next Steps for Managing Freshwater Resources in a Changing Climate summarizes recommendations for implementing the National Action Plan: Priorities for Managing Freshwater Resources in a Changing Climate. The report was developed by the Water Resources Adaptation to Climate Change Workgroup that supports the Advisory Committee on Water Information - a national federal advisory committee made up of representatives of a diverse set of stakeholders and federal agencies. The Workgroup organized five subgroups based on the major recommendation topics in the National Action Plan: data and information for decision-making; vulnerability assessment; water use efficiency and conservation; integrated water resource management; and capacity building in training and outreach. The report is the result of discussions that took place at a two-day meeting of the Workgroup members in February 2014.  

Arid Ecosystems

Annual Changes in Bluebunch Wheatgrass Biomass and Nutrients Related to Climate and Wildfire

Peek, James M. 2014. Annual Changes in Bluebunch Wheatgrass Biomass and Nutrients Related to Climate and Wildfire. Northwest Science 88(2): 129-139

Current year's growth (biomass) and nutrient levels of bluebunch wheatgrass (Pseudoroegneria spicata), a highly palatable bunchgrass in western North America, were evaluated over 20-year and 10-year periods, respectively. Three study sites representing a range of variation in conditions were located on south-facing slopes. Annual biomass ranged from 5.6 to 109.0 gm m-2 on individual sites with means for all sites of 42.7 gm m-2 (range 17.5–73.3 gm m-2), with April and May precipitation best predicting the variation. Variation was highest on the site lowest in elevation and highest in biomass. A fire in August 2000 that burned all study sites suppressed biomass for the following two years, aided by lower than average precipitation. The highest elevation site had higher mean values of Cu, Mg, N, K, P, S, and Zn than the two lower sites, but the greatest range of values occurred on one of the two lower sites for Ca, Fe, K, Mg, N, P, and S. Combinations of temperature and precipitation predicted Ca, K, N, P, and Zn values, while Cu and Fe were predicted with total monthly precipitation, and Mg and S were predicted with mean monthly temperature. Values of Cu, Fe, K, N, P, S, and Zn were higher than expected for one to two years following the 2000 fire, while Ca and Mg did not show any responses to the fire. Predictions for biomass and nutrient content apply to the range of conditions, temperatures and precipitation observed over the study period. The predictions may be useful in assessing responses to changes in climate, and are helpful in explaining variation in herbivore populations relative to changes in forage quality and quantity. 

Drought and Ecological Site Interaction on Plant Composition of a Semi-Arid Rangeland

Scasta, J. D., and B. S. Rector. 2014. Drought and Ecological Site Interaction on Plant Composition of a Semi-Arid Rangeland. Arid Land Research and Management 28:197-215

Fluctuating climatic patterns are increasing the frequency and severity of drought, a concern for native plant communities on grazed semi-arid rangelands. Vegetation successional models have focused on the impact of management and have failed to quantify the effects of extreme drought. From 2001 to 2011, plant community composition was sampled on ecological sites in a semi-arid rangeland managed with conservative grazing and frequent fire since 1937. Ordination and classification were used to assess the interactive effects of ecological site and extreme drought on plant species composition, holding all other external drivers constant. Deeper soil clay loam sites had 4x greater beta diversity than shallower and rockier low stony hill sites, an indication of greater species turnover and instability in response to extreme drought. Cumulative effects of drought years explained similarity between sites and species composition. Response to extreme drought varied by species; no response (Bouteloua curtipendula), decreased (Nassella leucotricha), and increased (Bouteloua rigidiseta and Eriochloa sericea). Annual C3 plant responses were explained by short-term drought and perennial C3 and C4 plant responses were explained by long-term drought. Clay loam sites had maximum species richness and diversity values during neutral periods with quadratic declines associated with climatic extremes (dry or wet) compared to the more xeric sites which had minimum species richness and diversity during neutral periods with quadratic increases during climatic extremes. The interaction between site and drought, holding all other external drivers constant, can enhance our understanding of plant community dynamics and secondary plant succession of degraded semi-arid rangelands. 

The effects of precipitation and soil type on three invasive annual grasses in the western United States

Bansal, S., J. J. James, and R. L. Sheley. 2014. The effects of precipitation and soil type on three invasive annual grasses in the western United States. Journal of Arid Environments 104:38-42

Multiple species of annual grasses are invading sagebrush-steppe communities throughout the western United States. Most research has focused on dominant species such as Bromus tectorum (cheatgrass), yet other, less studied annual grasses such as Taeniatherum caput-medusae (medusahead) and Ventenata dubia (ventenata) are spreading rapidly. Future precipitation regimes are expected to have less frequent but more intense rain events, which may affect soil moisture availability and favor these ‘newer’ invasives over cheatgrass. We conducted a full factorial, growth chamber study examining the effects of two watering regimes (small/frequent, large/infrequent rain pulses) across nine soil types on the growth of cheatgrass, medusahead and ventenata. We tested a hypothesis that medusahead or ventenata would have greater growth than cheatgrass with larger/infrequent rain events. The two watering regimes had relatively strong effects on soil water content, but generally did not impact plant growth. In contrast, variation in soil properties such as clay content, pH and soil N correlated with a two- to four-fold change in plant growth. The three invasive grass species generally respond similarly to changes in precipitation regimes and to edaphic factors. Nevertheless, medusahead had 30–40% overall greater root growth compared to the other species and a 15% increase in root growth in response to the large/infrequent watering treatment. Our findings reveal that 1) greater biomass allocation to roots and 2) greater responsiveness of root growth to differing precipitation regimes of medusahead may favor its ecological success over other invasive annuals under future climate scenarios. 

Biodiversity/Species and Ecosystem Response

Land management trumps the effects of climate change and elevated CO2 on grassland functioning

Aurélie Thébault, Pierre Mariotte, Christopher J. Lortie and Andrew S. MacDougall  Journal of Ecology Volume 102, Issue 4, pages 896–904, July 2014, DOI: 10.1111/1365-2745.12236

 A meta-analysis is used here to examine drivers at both scales primarily targeting services provided by grasslands relating to plant productivity (above- and below-ground biomass) and soil processes (nutrients and soil respiration) in 38 manipulative experiments published in the last decade. The authors specifically target effects of (i) single and combined land management practices (LMs), (ii) single and combined factors relating to broad-scale climate change and elevated CO2, and (iii) combined management practices and changes to climate and CO2.  Collectively, this examines the general efficacy of global change models in predicting changes to grassland functioning.  The authors found that combinations of management practices had approximately double the explanatory power for variation in grassland services compared with individual or interactive effects of factors associated with climate change and CO2.  Although this work confirms how climate change and CO2 can affect many ecosystem-based functional attributes, it suggests that combinations of land management practices remain the dominant set of factors in determining the performance of grassland plant communities. Land management may thus be critical for influencing projected responses to future climate change and elevated CO2 in models of grassland function at least for factors relating to primary production. 

Mechanisms underpinning climatic impacts on natural populations: altered species interactions are more important than direct effects

Ockendon, N., Baker, D. J., Carr, J. A., White, E. C., Almond, R. E. A., Amano, T., Bertram, E., Bradbury, R. B., Bradley, C., Butchart, S. H. M., Doswald, N., Foden, W., Gill, D. J. C., Green, R. E., Sutherland, W. J., Tanner, E. V. J. and Pearce-Higgins, J. W. (2014), Mechanisms underpinning climatic impacts on natural populations: altered species interactions are more important than direct effects. Global Change Biology, 20: 2221–2229. doi: 10.1111/gcb.12559

Shifts in species' distribution and abundance in response to climate change have been well documented, but the underpinning processes are still poorly understood. This paper provides the results of a systematic literature review and meta-analysis investigating the frequency and importance of different mechanisms by which climate has impacted natural populations. Most studies were from temperate latitudes of North America and Europe; almost half investigated bird populations. Significantly greater support for indirect, biotic mechanisms were found than direct, abiotic mechanisms as mediators of the impact of climate on populations. In addition, biotic effects tended to have greater support than abiotic factors in studies of species from higher trophic levels. For primary consumers, the impact of climate was equally mediated by biotic and abiotic mechanisms, whereas for higher level consumers the mechanisms were most frequently biotic, such as predation or food availability. Biotic mechanisms were more frequently supported in studies that reported a directional trend in climate than in studies with no such climatic change, although sample sizes for this comparison were small. The authors call for more mechanistic studies of climate change impacts on populations, particularly in tropical systems. 

The subtle role of climate change on population genetic structure in Canada lynx

Row, J. R., Wilson, P. J., Gomez, C., Koen, E. L., Bowman, J., Thornton, D. and Murray, D. L. (2014), The subtle role of climate change on population genetic structure in Canada lynx. Global Change Biology, 20: 2076–2086. doi: 10.1111/gcb.12526

This research shows that current genetic variability of Canada lynx is strongly correlated with a winter climate gradient (i.e. increasing snow depth and winter precipitation from west-to-east) across the Pacific-North American (PNO) to North Atlantic Oscillation (NAO) climatic systems. This relationship was stronger than isolation by distance and not explained by landscape variables or changes in abundance. Thus, these patterns suggest that individuals restricted dispersal across the climate boundary, likely in the absence of changes in habitat quality. We propose habitat imprinting on snow conditions as one possible explanation for this unusual phenomenon. Coupling historical climate data with future projections, we also found increasingly diverging snow conditions between the two climate systems. Based on genetic simulations using projected climate data (2041–2070), we predicted that this divergence could lead to a threefold increase in genetic differentiation, potentially leading to isolated east–west populations of lynx in North America. Our results imply that subtle genetic structure can be governed by current climate and that substantive genetic differentiation and related ecological divergence may arise from changing climate patterns.

Exotic plant invasions under enhanced rainfall are constrained by soil nutrients and competition

Anu Eskelinen and Susan Harrison. 2014. Exotic plant invasions under enhanced rainfall are constrained by soil nutrients and competition. Ecology 95:682–692. http://dx.doi.org/10.1890/13-0288.1

To predict the net impact of climate change on invasions, it is critical to understand how its effects interact with environmental and biotic context. In a factorial field experiment, we examined how increased late-season rainfall influences the growth and reproductive success of two widespread invasive species (Centaurea solstitialis and Aegilops triuncialis) in heterogeneous Californian grasslands, and, in particular, how its impact depends on habitat type, nutrient addition, and competition with resident species. Rainfall enhancement alone exhibited only weak effects, especially in naturally infertile and relatively uninvaded grasslands. In contrast, watering and fertilization together exhibited highly synergistic effects on both invasive species. However, the benefits of the combined treatment were greatly reduced or offset by the presence of surrounding competitors. Our results highlight the roles of nutrient limitation and biotic resistance by resident competitors in constraining the responses of invasive species to changes in rainfall. In systems with strong environmental control by precipitation, enhanced rainfall may promote invasions mainly under nutrient-rich and disturbed conditions, while having lesser effects on nutrient-poor, native “refuges.” 

Amphibians in the climate vise: loss and restoration of resilience of montane wetland ecosystems in the western US

Maureen E Ryan, Wendy J Palen, Michael J Adams, and Regina M Rochefort 2014. Amphibians in the climate vise: loss and restoration of resilience of montane wetland ecosystems in the western US. Frontiers in Ecology and the Environment 12: 232–240. http://dx.doi.org/10.1890/130145

Amphibians in the West’s high-mountain areas find themselves in a vise, caught between climate-induced habitat loss and predation from introduced fish. This North Pacific LCC-backed project developed a list of tools that could be of use to land managers working with montane wetlands including a hydrologic model and remote-sensing techniques. 

Causes of warm-edge range limits: systematic review, proximate factors and implications for climate change

Cahill, A. E., M. E. Aiello-Lammens, M. Caitlin Fisher-Reid, X. Hua, C. J. Karanewsky, H. Y. Ryu, G. C. Sbeglia, F. Spagnolo, J. B. Waldron, and J. J. Wiens. 2014. Causes of warm-edge range limits: systematic review, proximate factors and implications for climate change. Journal of Biogeography 41:429-442

The factors that set species range limits underlie many patterns in ecology, evolution, biogeography and conservation. These factors have been the subject of several reviews, but there has been no systematic review of the causes of warm-edge limits (low elevations and latitudes). Although it is often assumed that warm-edge limits are set by biotic factors, our review shows that abiotic factors (primarily temperature) are supported more often among the species in these 125 studies. However, few studies both identify proximate causes and test alternative mechanisms, or examine the interaction between biotic and abiotic factors. Filling these gaps should be a high priority as warm-edge populations are increasingly driven to extinction by climate change.  

Snowshoe hares display limited phenotypic plasticity to mismatch in seasonal camouflage

Zimova, M., L. S. Mills, P. M. Lukacs, and M. S. Mitchell. 2014. Snowshoe hares display limited phenotypic plasticity to mismatch in seasonal camouflage. Proceedings of the Royal Society B: Biological Sciences 281. doi: 10.1098/rspb.2014.0029

Plasticity in moult phenology and behaviours in snowshoe hares has been found to be insufficient for adaptation to camouflage mismatch, suggesting that any future adaptation to climate change will require natural selection on moult phenology or behaviour….  As duration of snow cover decreases owing to climate change, species undergoing seasonal colour moults can become colour mismatched with their background. The immediate adaptive solution to this mismatch is phenotypic plasticity, either in phenology of seasonal colour moults or in behaviours that reduce mismatch or its consequences. Researchers observed nearly 200 snowshoe hares across a wide range of snow conditions and two study sites in Montana, USA, and found minimal plasticity in response to mismatch between coat colour and background. It was found that moult phenology varied between study sites, likely due to differences in photoperiod and climate, but was largely fixed within study sites with only minimal plasticity to snow conditions during the spring white-to-brown moult. No evidence was found that hares modify their behaviour in response to colour mismatch. Hiding and fleeing behaviours and resting spot preference of hares were more affected by variables related to season, site and concealment by vegetation, than by colour mismatch. 

Change is coming to the northern oceans

Anne B. Hollowed and Svein Sundby, Science 6 June 2014: 344 (6188), 1084-1085. [DOI:10.1126/science.1251166]

The cold-temperate regions of the North Pacific and North Atlantic oceans, from about 40°N latitude to the Arctic fronts, support large and productive fisheries (1), particularly in the northernmost regions: the Bering Sea in the Pacific and the Barents Sea in the Atlantic. The two main near-bottom fish species in the Bering and Barents seas are walleye pollock (Gadus chalcogrammus) and Atlantic cod (G. morhua), respectively. In the past decade, the two species have responded differently to ocean warming. These response patterns appear to be linked to a complex suite of climatic and oceanic processes that may portend future responses to warming ocean conditions. 

Conservation blueprint completed for Columbia Plateau Ecoregion

To aid managers in strategic conservation efforts in the Columbia Plateau Ecoregion, the Great Northern LCC funded a two-year landscape conservation design project. The recently completed project, led by the US Fish & Wildlife Service's National Wildlife Refuge planning office, and in collaboration with the Arid Lands Initiative, used spatial analyses to identify priority areas for restoration and protection of habitats and species. This will allow conservation partners to work from a common blueprint for on-the-ground conservation actions and in developing management strategies adapted to a changing climate.  

Precipitation, not warming temperatures, may be key in bird adaptation to climate change

 Illán, J. G., Thomas, C. D., Jones, J. A., Wong, W.-K., Shirley, S. M. and Betts, M. G. (2014), Precipitation and winter temperature predict long-term range-scale abundance changes in Western North American birds. Global Change Biology. doi: 10.1111/gcb.12642

A new empirically-based model analyzing how birds in western North America will respond to climate change suggests that for most species, regional warming is not as likely to influence population trends as will precipitation changes. Several past studies have found that temperature increases can push some animal species – including birds – into higher latitudes or higher elevations. Few studies, however, have tackled the role that changes in precipitation may cause. This analysis finds that for many species, it is precipitation that most affects the long-term survival of many bird species due to associated changes plant growth, soil moisture, water storage and insect abundance and distributions. The researchers examined long-term data on bird distributions and abundance covering five states in the western United States, and in the Canadian province of British Columbia, testing statistical models to predict temporal changes in population of 132 bird species over a 32-year period. They analyzed the impacts of temperature and precipitation on bird distributions at the beginning of the study period (the 1970s) and then tested how well the predictions performed against actual population trends over the ensuing 30 years. 

Climate and Weather Reports and Services

NOAA Climate Connection E-Newsletter

Free monthly e-newsletter designed to increase climate literacy and communication capacity for NOAA and its partners. Subscription requests can be sent to NOAAClimateConnection@noaa.govClick here to view the June 2013 NOAA Climate Connection e-newsletter.

Office of the Washington State Climatologist issues a monthly newsletter

The Office of the Washington State Climatologist issues a monthly newsletter that summarizes the WA climate for the previous month, includes a precipitation and temperature outlook, and also includes a brief summary of an interesting aspect of the weather or climate of WA, among a few other sections. 

NOAA 2013 Global Climate Report

The average global temperature for 2013 tied as the fourth warmest year since record keeping began in 1880, according to NOAA scientists. It also marked the 37th consecutive year with a global temperature above the 20th century average. The last below-average annual temperature was 1976. Including 2013, all 13 years of the 21st century (2001-2013) rank among the 15 warmest in the 134-year period of record.  The three warmest years on record are 1998, 2005, and 2010.  This analysis is from NOAA's National Climatic Data Center in Asheville, North Carolina.  

Great Basin Weather and Climate Dashboard

This website provides up to date climate and weather data and forecasts/outlooks for the Great Basin including temperature, precipitation, drought, snowpack and hydrologic information.  (Some of the information includes the entire western U.S.)  The Dashboard is a joint effort amongst the Western Regional Climate Center, California and Nevada Applications Program, the USDA Farm Service Agency and the Great Basin LCC

Coastal/Marine Ecosystems, Ocean Acidification, Sea Level Rise

Key Lessons for Incorporating Natural Infrastructure into Regional Climate Adaptation Planning

Langridge et al., Ocean & Coastal Manage, Volume 95, July 2014, Pages 189–197, DOI: 10.1016/j.ocecoaman.2014.03.019

A new article in Ocean & Coastal Management details a collaborative process in two coastal California counties to account for the role of natural infrastructure in climate adaptation planning. 

For Corals Adapting to Climate Change, It’s Survival of the Fattest—and Most Flexible

Grottoli, A. G., Warner, M. E., Levas, S. J., Aschaffenburg, M. D., Schoepf, V., McGinley, M., Baumann, J. and Matsui, Y. (2014), The cumulative impact of annual coral bleaching can turn some coral species winners into losers. Global Change Biology. doi: 10.1111/gcb.12658

The future health of the world’s coral reefs and the animals that depend on them relies in part on the ability of one tiny symbiotic sea creature to get fat—and to be flexible about the type of algae it cooperates with. In the first study of its kind, scientists at The Ohio State University discovered that corals—tiny reef-forming animals that live symbiotically with algae—are better able to recover from yearly bouts of heat stress, called “bleaching,” when they keep large energy reserves—mostly as fat—socked away in their cells. 


Wildland fire emissions, carbon, and climate: Wildfire–climate interactions

Yongqiang Liu, Scott Goodrick, Warren Heilman, journal Forest Ecology and Management, Volume 317, Pages 1-96 (1 April 2014)

ncreasing wildfire activity in recent decades, partially related to extended droughts, along with concern over potential impacts of future climate change on fire activity has resulted in increased attention on fire–climate interactions. Findings from studies published in recent years have remarkably increased our understanding of fire–climate interactions and improved our capacity to delineate probable future climate change and impacts. Fires are projected to increase in many regions of the globe under a changing climate due to the greenhouse effect. Burned areas in the western US could increase by more than 50% by the middle of this century. Increased fire activity is not simply an outcome of the changing climate, but also a participant in the change. Smoke particles reduce overall solar radiation absorbed by the Earth’s atmosphere during individual fire events and fire seasons, leading to regional climate effects including reduction in surface temperature, suppression of cloud and precipitation, and enhancement of climate anomalies such as droughts. Black carbon (BC) in smoke particles displays some different radiation and climate effects by warming the middle and lower atmosphere, leading to a more stable atmosphere. BC also plays a key role in the smoke-snow feedback mechanism. Fire emissions of CO2, on the other hand, are an important atmospheric CO2 source and contribute substantially to the global greenhouse effect. Future studies should generate a global picture of all aspects of radiative forcing by smoke particles. Better knowledge is needed in space and time variability of smoke particles, evolution of smoke optical properties, estimation of smoke plume height and vertical profiles and their impacts on locations of warming layers, stability structure, clouds and smoke transport, quantification of BC emission factors and optical properties from different forest fuels, and BC’s individual and combined roles with organic carbon. Finally, understanding the short- and long-term greenhouse effect of fire CO2 emissions, increased capacity to project future fire trends (especially mega-fires), with consideration of climate–fuel–human interactions, and improved fire weather and climate prediction skills (including exploring the SST-fire relations) remain central knowledge needs. 


Northern Rockies Adaptation Partnership

Northern Rockies Adaptation Partnership is a new US Forest Service led science-management collaboration with the goals of: 1)Assessing vulnerability of natural resources and ecosystem services to climate change; and 2)Developing science-based adaptation strategies that can be used by national forests to understand and mitigate the negative effects of climate change. 

Blue Mountains Adaptation Partnership

Blue Mountains Adaptation Partnership is a new US Forest Service led science-management collaboration with the goals of: Increasing climate change awareness; Assessing vulnerability of cultural and natural resources; and Developing science-based adaptation strategies and incorporating them into management of federal lands in the Blue Mountains

Climate effects on Western U.S. Forests

USGS scientists and colleagues attempted to identify which mechanism dominates climate-related changes in tree mortality across the landscape. Using data from a long-term study of tree demography in the Sierra Nevada of California, they found strong evidence that the drivers of changing mortality rates differ between forests where growth is limited by energy (colder, wetter areas with shorter growing seasons) and forests where growth is limited by water (hotter, drier areas where water is more scarce). In water-limited forests, drought stress on trees seems to dominate changes in mortality rate, while in energy-limited forests climatic effects on tree-killing organisms also appear to play a key role. However, they also discovered that currently available data are inadequate to clearly forecast how these mechanisms will affect tree mortality in the future, with different (and equally supported) models giving radically different outcomes. The paper was published in the journal PLOS One and is available here

Special Reports / Announcements

NASA's new satellite, OCO-2, launched July 2

OCO-2 is NASA's first satellite dedicated to measuring atmospheric CO2.  It is designed to collect space-based global measurements of atmospheric CO2 with the precision, resolution, and coverage needed to characterize sources and sinks on regional scales.  OCO-2 joins five other Earth-observing satellites rush along like trains on the same "track," flying minutes, and sometimes seconds, behind one another. They carry more than 15 scientific instruments in total, looking at many different aspects of our home planet. Called the Afternoon Constellation, or A-Train, these satellites work as a united, powerful tool for advancing our understanding of Earth's surface and atmosphere.  OCO-2 and other measurements will be combined with data from a ground-based network to provide scientists with the information they need to better understand the processes that regulate atmospheric CO2 and its role in the carbon cycle. This enhanced understanding is essential for improving predictions of future atmospheric CO2 increases and its impact on Earth's climate.

Recent increases in extreme temperature occurrence over land

Weaver, S. J., A. Kumar, and M. Chen (2014), Recent increases in extreme temperature occurrence over land, Geophys. Res. Lett., 41, doi:10.1002/2014GL060300

This research indicates that the increasing global and U.S. temperatures over the last 30 years are predominantly the result of shifts in the mean temperature distribution and not increasing temperature variability. As such, the likelihood of increases in the occurrence of warm temperature extremes will likely continue to increase worldwide, leading to significant impacts on many socioeconomic sectors such as agriculture and public health.  

Another Drop in Water Vapor

Urban, J., S. Lossow, G. Stiller and W. Read (2014), Another Drop in Water Vapor, Eos Trans. AGU, 95(27), 245

In 2000 a sudden severe drop in stratospheric water vapor levels interrupted the supposed long-term increase of this greenhouse gas, an important contributor to global warming and climate variability. Satellite sensors observed a recovery in the following years, hidden behind a large variability. More recently, during 2011 and 2012, measurements revealed another severe drop in stratospheric water vapor concentrations. Similar abrupt changes have likely occurred previously but were not observed because of the lack of adequate satellite measurements before the 1990s. In addition, future changes may remain unobserved, with present- day limb- sounding satellites well beyond their design lifetimes and no new missions planned to continue the observation record. 

Preindustrial land use change caused 0.73°C of global warming

Summary excerpt from Eos, Vol. 95, No. 26, 1 July 2014; He et al., Geophysical Research Letters, doi:10.1002/ 2013GL058085, 2014

Since the dawn of the Holocene nearly 12,000 years ago, humans have been shaping the Earth’s surface and atmosphere. By redistributing soil and nutrients, clearing land, chopping down trees, rerouting rivers, setting fires, and, later, burning fossil fuels, humans have gradually become the dominant driver of change in the Earth’s climate.  Through widespread land use change—first for agriculture and later through urbanization humans have gradually changed the balance of the global energy budget. Using a global climate model, He et al. have figured out how the land- clearing practices of preindustrial civilizations affected the Earth’s temperature….  They found that by influencing biogeophysical systems, Holocene era land use change caused… a net 0.73°C of warming caused by preindustrial land use change. By comparison, the authors note, the post-industrial era has seen 0.8°C of anthropogenic global warming (in a much shorter time period). 

Taking Action

Connect with the American Society of Adaptation Professionals

The American Society of Adaptation Professionals (ASAP) connects leading professionals from a variety of sectors working to increase climate resilience across the United States.  Initially created in 2011, and formally launched in 2013, ASAP provides a platform and forum for climate adaptation leaders to interact, participate in cutting edge research, develop guidance for adaptation, and collaborate with their colleagues across the country.  The society builds off the strengths of its members and focuses on connecting adaptation professionals across the United States. Membership is free for 2014.  

Interactive Tool Lets You Decide How to Reduce Emissions

What can we do to limit the magnitude of climate change? How would you reduce the nation's greenhouse gas emissions? A new interactive tool from the Koshland Science Museum of the National Academy of Sciences lets you decide. The goal in the tool scenario is to reduce cumulative U.S. greenhouse emissions to 203 gigatons or less by the year 2050. The tool asks you to set priorities among cost-savings, land preservation, oil independence, air quality, or a combination and then to choose a portfolio of renewable energy, carbon capture, land use, and other options to safeguard those priorities while achieving target emission levels. Try it today! 

What are the greenhouse gas emissions for your diet?

A new study finds the average greenhouse gas emissions GHG emissions (in kilograms of carbon dioxide equivalents per day) of meat-eaters, fish-eaters, vegetarians and vegans were: 7.19 for high meat-eaters, 5.63 for medium meat-eaters, 4.67 for low meat-eaters, 3.91 for fish-eaters, 3.81 for vegetarians and 2.89 for vegans.