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Hi All, February 2025 brought a wide range of weather to Tennessee including severe storms, snow, flooding, and large temperature fluctuations. Warm temperatures in the first week of the month brought a taste of spring after a much colder than normal January across the state, with high temperatures climbing into the upper 70’s for many locations on February 4th. This warm airmass set the stage for severe weather to impact northern areas of the state on February 6th, with six reports of tornadoes (four EF1 tornadoes and two EF2 tornadoes). Cooler and wetter weather then returned to the state for the middle of February, with another round of severe weather impacting the state on February 15th, with one tornado in Gibson County. The same storm system then set up heavy rains across West Tennessee, northern portions of Middle Tennessee, and across Kentucky and southwest Virginia. Two-day rainfall totals from February 15-16 were in the range of 5-8-inches across northern counties of West and Middle Tennessee, which produced several instances of flash flooding and river floods. A flash flood emergency was issued by the National Weather Service-Memphis office as water quickly inundated the town of Rives, in Obion County, due to a levee being overtopped on the Obion River on February 16th. Around 200 people evacuated, including 100 people who were brought to safety by swift water rescue teams. Another round of winter weather and very cold air impacted the state on February 20/21, with snowfall of 1-3-inches and record-setting cold temperatures (high temperatures struggled to get out of the teens or 20s). The cold was quickly replaced by warmer weather and many locations saw their hottest temperatures of the month within a week of the cold blast. The Nashville International Airport recorded a high of 80°F on February 26, the 7th earliest 80-degree day in the airport station’s history, which dates back to 1940. Happy *almost* Spring! Andrew & Wil Tennessee Climate Office East Tennessee State University Department of Geosciences 310 Ross Hall Johnson City, TN 37614

This study examines the spatial and temporal characteristics of the surface air temperature in Portland, Oregon. Spatial temperature patterns indicate that the dominant control factors on seasonal temperature distribution are local topography, elevation, and urban-rural differences in surface structure. A heat island exists in the Portland area; the intensity of the heat island rang€s from 4° to 10° F, and varies throughout the year. The strongest heat island is found in the July minimum temperature. Temperature distribution in Portland and the adjacent area is affected by winds and rainy conditions, but less influenced under overcast skies. The long-term temperature over the last century shows that Portland's mean annual temperature trends are 0.057° F/yr and 0.052° F/yr in the two warming periods 1900-1940 and 1961-1984, respectively, and these warming trends are largely due to warming in spring and early summer as well as in winter months except January. Comparisons between Portland and other local non-urban climatic stations show a general warming trend in Portland since the end of the last century, which is 0.028° F/yr in the mean annual temperature, and 0.017° F/yr in maximum temperature after the regional trends are removed. Monthly mean temperature in July and January demonstrate a warming by 0.023° F/yr and 0.015° F/yr at Portland, respectively. All these warming trends are due mainly to the impact of urbanization. It is found that the cooling effect on the northern Willamette Valley due to the presence of the Columbia Gorge is most noticeable in the daytime and in January.

Local climate action plans have become more prevalent in recent years yet information on their success is limited. While unlikely, on their own, to be able to mitigate enough carbon emissions to prevent catastrophic impacts of global temperature increase, local climate planning has the potential to play an important role in a number of key ways. Cities have traditionally exercised control in areas that have GHG abatement potential at low cost (e.g. building codes, land use, energy procurement) and the total population represented by cities committed to GHG reduction efforts is not insignificant and continues to grow. The extent to which local climate plans can serve as a meaningful element in a larger (but currently woefully inadequate) policy picture, will depend on their ability to set aggressive goals, dedicate resources, test innovative strategies, and measure progress systematically. Looking at the plans and progress reports of five U.S. cities, many have set aggressive goals and created innovative programs that could be replicated at other levels of government, but most are somewhat lacking in measuring and reporting progress metrics and financial resources committed to these efforts. For local climate planning to contribute significantly to broader climate policy, it will need to develop more rigorous progress metrics so the highest yield, lowest cost abatement strategies can be identified and advanced in other cities and at higher levels of government. / text

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

The climate of the eastern section of the Sahelian latitude, especially over the Eritrean subdomain, is often associated with long drought episodes from which the atmospheric mechanisms are poorly understood. In an effort to improve our knowledge of weather and climate systems over this region, the PRECIS Regional Climate Model (RCM) from the United Kingdom (UK) was obtained and implemented. Such a climate model that is based upon the physical laws of nature has the ability to simulate regional-scale atmospheric patterns, and therefore, may significantly contribute to our understanding of local atmospheric processes. In this dissertation the assessment of past regional climate trends from both observations and model simulations, and the simulation of scenarios for possible future climate change were regarded as important. To investigate this, the PRECIS RCM was first nested over the Eritrean domain into the “atmosphere only” HadAM3H global General Circulation Model (GCM) and forced at its lateral boundaries by a 30-year present-day (1961-1990) integration of the same global model. Secondly, the PRECIS RCM was constrained at its lateral boundary by the “fully coupled” HadCM3 GCM (for Sea Surface Temperatures (SSTs) and sea-ice) and its improved atmospheric component (HadAM3H GCM). The latter simulations provided boundary conditions for the A2 and B2 future emission scenarios (Special Report on Emission Scenarios (SRES)) to simulate a 20-year (2070-2090) projection of future climate. These experiments allowed for verification of both spatial and temporal present-day climate simulations, as well as possible future climate trends as simulated by the PRECIS RCM over the Eritrean domain, with specific emphasis on temperature and moisture related variables. The study indicates that PRECIS RCM climate simulations are mostly in harmony with observed spatial patterns. This skill may be attributed to the full representation of the climatic system (land surface, sea, ice, atmosphere and atmospheric chemistry such as sulphur and greenhouse gasses) in the model configuration. However, when comparing PRECIS RCM results with the much coarser resolution (2.5ox2.5o) National Centre for Environmental Prediction (NCEP) reanalysis data, obvious differences do occur. These differences are not necessarily the result of poor model performance, but may be attributed to more detailed simulations over the finer RCM grid (0.44o x 0.44o). Future climate scenario simulation with the PRECIS RCM over Eritrea produce increased surface temperature in both the A2 and B2 SRES scenario integrations, relative to the present climatology. This temperature increase also appears in the driving GCM (HadCM3) as well as in other GCM results from the Inter Governmental Panel for Climate Change (IPCC) initiative. There are, however, mixed signals in rainfall projections. According to PRECIS RCM results, rainfall is expected to increase in most of the Eritrean region. Copyright 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beraki, A F 2005, Climate change scenario simulations over Eritrea by using a fine resolution limited area climate model : temperature and moisture sensitivity , MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-02102006-152327 / > / Dissertation (MSc)--University of Pretoria, 2007. / Geography, Geoinformatics and Meteorology / Unrestricted

Previous research indicates a distinct seasonal pattern in mortality rates. Increases are prominent during the northern-hemispheric cold season. These patterns are seen in overall mortality, diabetes mellitus, circulatory, digestive, and respiratory diseases. A principal component analysis indicates that departure from normal temperature, minimum, maximum, and average daily temperature, and dew-point temperature are the primary atmospheric variables that influence mortality patterns. ANOVA and Kruskal-Wallis tests support findings of principal component analysis. Although a day-to-day relationship between mortality rates and atmospheric variables was noted in several instances, results suggest that the influence of the primary atmospheric variables on mortality rates is greatest when a three to five-day lag time is in place. Furthermore, results indicate that the combination of these variables in conjunction with frontal passage is linked to seasonal increases in mortality. A combination of atmospheric variables that influence mortality rates has been identified, however, their exact influence is still unclear.

This master’s thesis examines aspects of climate change discourse in the news coverage of the climate summit COP28 in the UK’s The Guardian, Germany’s Die Zeit and Sweden’s Dagens Nyheter. Approaching the connection between COP28 and discourse contributes to field of media and climate change as well as climate journalism. By deploying content analysis and critical discourse analysis, my study follows the structure of an explanatory sequential mixed methods design. Analysing 138 articles from The Guardian, Die Zeit and Dagens Nyheter about COP28, this thesis offers an overview and an in-depth exploration of summit themes, voices and discourses. Findings suggest a centring on the theme of fossil fuels in connection to a discourse on human related exploitation of resources and emissions as well as environmental damages. A turn to political and scientific authority voices is noticeable and the Global North’s responsibility remains detached from climate action and climate policy.

Here we analyze climate variability using instrumental, paleoclimate (proxy), and the latest climate model data to understand more about the sources and impacts of low-frequency climate variability. Understanding the drivers of climate variability at interannual to century timescales is important for studies of climate change, including analyses of detection and attribution of climate change impacts. Additionally, correctly modeling the sources and impacts of variability is key to the simulation of abrupt change (Alley et al., 2003) and extended drought (Seager et al., 2005; Pelletier and Turcotte, 1997; Ault et al., 2014). In Appendix A, we employ an Earth system model (GFDL-ESM2M) simulation to study the impacts of a weakening of the Atlantic meridional overturning circulation (AMOC) on the climate of the American Tropics. The AMOC drives some degree of local and global internal low-frequency climate variability (Manabe and Stouffer, 1995; Thornalley et al., 2009) and helps control the position of the tropical rainfall belt (Zhang and Delworth, 2005). We find that a major weakening of the AMOC can cause large-scale temperature, precipitation, and carbon storage changes in Central and South America. Our results suggest that possible future changes in AMOC strength alone will not be sufficient to drive a large-scale dieback of the Amazonian forest, but this key natural ecosystem is sensitive to dry-season length and timing of rainfall (Parsons et al., 2014). In Appendix B, we compare a paleoclimate record of precipitation variability in the Peruvian Amazon to climate model precipitation variability. The paleoclimate (Lake Limón) record indicates that precipitation variability in western Amazonia is ‘red’ (i.e., increasing variability with timescale). By contrast, most state-of-the-art climate models indicate precipitation variability in this region is nearly'‘white' (i.e., equally variability across timescales). This paleo-model disagreement in the overall structure of the variance spectrum has important consequences for the probability of multi-year drought. Our lake record suggests there is a significant background threat of multi-year, and even decade-length, drought in western Amazonia, whereas climate model simulations indicate most droughts likely last no longer than one to three years. These findings suggest climate models may underestimate the future risk of extended drought in this important region. In Appendix C, we expand our analysis of climate variability beyond South America. We use observations, well-constrained tropical paleoclimate, and Earth system model data to examine the overall shape of the climate spectrum across interannual to century frequencies. We find a general agreement among observations and models that temperature variability increases with timescale across most of the globe outside the tropics. However, as compared to paleoclimate records, climate models generate too little low-frequency variability in the tropics (e.g., Laepple and Huybers, 2014). When we compare the shape of the simulated climate spectrum to the spectrum of a simple autoregressive process, we find much of the modeled surface temperature variability in the tropics could be explained by ocean smoothing of weather noise. Importantly, modeled precipitation tends to be similar to white noise across much of the globe. By contrast, paleoclimate records of various types from around the globe indicate that both temperature and precipitation variability should experience much more low-frequency variability than a simple autoregressive or white-noise process. In summary, state-of-the-art climate models generate some degree of dynamically driven low-frequency climate variability, especially at high latitudes. However, the latest climate models, observations, and paleoclimate data provide us with drastically different pictures of the background climate system and its associated risks. This research has important consequences for improving how we simulate climate extremes as we enter a warmer (and often drier) world in the coming centuries; if climate models underestimate low-frequency variability, we will underestimate the risk of future abrupt change and extreme events, such as megadroughts.

The current cycle of climate change along with increases in hurricane activity, changing precipitation patterns, glacial melt, and other extremes of weather has led to interest and research into the global correlation or teleconnection between these events. Examination of historical climate records, proxies and observations is leading to formulation of hypotheses of climate dynamics with modeling and simulation being used to test these hypotheses as well as making projections. Ocean currents are believed to be an important factor in climate change with thermohaline circulation (THC) fluctuations being implicated in past cycles of abrupt change. Freshwater water discharge into high-latitude oceans attributed to changing precipitation patterns and glacial melt, particularly the North Atlantic, has also been associated with historical abrupt climate changes and is believed to have inhibited or shut down the THC overturning mechanism by diluting saline surface waters transported from the tropics. Here we analyze outputs of general circulation model (GCM) simulations parameterized by different levels of freshwater flux (no flux (control), 0.1 Sverdrup (Sv) and 1.0 Sv) with respect to tropical cyclone-like vortices (TCLVs) to determine any trend in simulated tropical storm frequency, duration, and location relative to flux level, as well as considering the applicability of using GCMs for tropical weather research. Increasing flux levels produced fewer storms and storm days, increased storm duration, a southerly and westerly shift (more pronounced for the 0.1 Sv level) in geographic distribution and increased activity near the African coast (more pronounced for the 1.0 Sv level). Storm intensities and tracks were not realistic compared to observational (real-life) values and is attributed to the GCM resolution not being fine enough to realistically simulate storm (microscale) dynamics.