Charlotte Wickham

A New Estimate of the AverageEarth Surface Land TemperatureSpanning 1753 to 2011

A New Estimate of the Average Earth Surface Land Temperature Spanning 1753 to 2011 We report an estimate of the Earth’s average land surface temperature for the period 1753 to 2011. To address issues of potential station selection bias, we used larger sampling of stations than having prior studies. For the period post 1880, our estimate is similar to those previously reported by other groups, although we report smaller error uncertainties. The land temperature rise from the 1950s decade to the 2000s decade is 0.90 ± 0.05°C (95% confidence).

Berkeley Earth Temperature Averaging Process

Berkeley Earth Temperature Averaging Process A new mathematical framework is presented for producing maps and large-scale averages of temperature changes from weather station thermometer data for the purposes of climate analysis. The method allows inclusion of short and discontinuous temperature records, so nearly all digitally archived thermometer data can be used. The framework uses the statistical method known as Kriging to interpolate data from stations to arbitrary locations on the Earth.

A likelihood-based time series modeling approach for application in dendrochronology to examine the growth-climate relations and forest disturbance history

A time series intervention analysis (TSIA) of dendrochronological data to infer the tree growth-climate-disturbance relations and forest disturbance history is described. Maximum likelihood is used to estimate the parameters of a structural time series model with components for climate and forest disturbances (i.e., pests, diseases, fire). The statistical method is illustrated with a tree-ring width time series for a mature closed-canopy Douglas-fir stand on the west slopes of the Cascade Mountains of Oregon, USA that is impacted by Swiss needle cast disease caused by the foliar fungus, Phaecryptopus gaeumannii (Rhode) Petrak. The likelihood-based TSIA method is proposed for the field of dendrochronology to understand the interaction of temperature, water, and forest disturbances that are important in forest ecology and climate change studies.

Regional patterns of increasing Swiss needle cast impacts on Douglas-fir growth with warming temperatures

Abstract The fungal pathogen, Phaeocryptopus gaeumannii, causing Swiss needle cast (SNC) occurs wherever Douglas‐fir is found but disease damage is believed to be limited in the U.S. Pacific Northwest (PNW) to the Coast Range of Oregon and Washington (Hansen et al., Plant Disease, 2000, 84, 773; Rosso & Hansen, Phytopathology, 2003, 93, 790; Shaw, et al., Journal of Forestry, 2011, 109, 109). However, knowledge remains limited on the history and spatial distribution of SNC impacts in the PNW. We reconstructed the history of SNC impacts on mature Douglas‐fir trees based on tree‐ring width chronologies from western Oregon. Our findings show that SNC impacts on growth occur wherever Douglas‐fir is found and is not limited to the coastal fog zone. The spatiotemporal patterns of growth impact from SNC disease were synchronous across the region, displayed periodicities of 12–40 years, and strongly correlated with winter and summer temperatures and summer precipitation. The primary climatic factor limiting pathogen dynamics varied spatially by location, topography, and elevation. SNC impacts were least severe in the first half of the 20th century when climatic conditions during the warm phase of the Pacific Decadal Oscillation (1924–1945) were less conducive to pathogen development. At low‐ to mid‐elevations, SNC impacts were most severe in 1984–1986 following several decades of warmer winters and cooler, wetter summers including a high summer precipitation anomaly in 1983. At high elevations on the west slope of the Cascade Range, SNC impacts peaked several years later and were the greatest in the 1990s, a period of warmer winter temperatures. Climate change is predicted to result in warmer winters and will likely continue to increase SNC severity at higher elevations, north along the coast from northern Oregon to British Columbia, and inland where low winter temperatures currently limit growth of the pathogen. Our findings indicate that SNC may become a significant forest health problem in areas of the PNW beyond the coastal fog zone.

Scenario‐Based and Scenario‐Neutral Assessment of Climate Change Impacts on Operational Performance of a Multipurpose Reservoir

Scenario-based and scenario-neutral impacts assessment approaches provide complementary information about how climate change-driven effects on streamflow may change the operational performance of multipurpose dams. Examining a case study of Cougar Dam in Oregon, United States, we simulated current reservoir operations under scenarios of plausible future hydrology. Streamflow projections from the CGCM3.1 general circulation model for the A1B emission scenario were used to generate stochastic reservoir inflows that were then further perturbed to simulate a potentially drier future. These were then used to drive a simple reservoir model. In the scenario-based analysis, we found reservoir operations are vulnerable to climate change. Increases in fall and winter inflow could lead to more frequent flood storage, reducing flexibility to store incoming flood flows. Uncertainty in spring inflow volume complicates projection of future filling performance. The reservoir may fill more or less often, depending on whether springs are wetter or drier. In the summer, drawdown may occur earlier to meet conservation objectives. From the scenario-neutral analysis, we identified thresholds of streamflow magnitude that can predict climate change impacts for a wide range of scenarios. Our results highlight projected operational challenges for Cougar Dam and provide an example of how scenario-based and scenario-neutral approaches may be applied concurrently to assess climate change impacts.