Andrew Emory Dessler

I write to oppose the proposed amendment as drafted. It should be rejected because its restrictions will exclude scientifically useful information from federal risk assessment. The amendment rests on two false premises: 1) that NCA5 presents RCP8.5 and SSP5-8.5 results as expected, baseline, or business-as-usual futures, and 2) that RCP8.5/SSP5-8.5 scenario runs are not useful for policy deliberations. As described here, neither of these premises is true. First, NCA5 accurately describes RCP8.5/SSP5-8.5 as very high emissions scenarios throughout the report. Second, because of uncertainty in many climate parameters (e.g., climate sensitivity), the temperatures produced under RCP8.5/SSP5-8.5 are a reasonable upper bound on what the future climate might be. These scenarios are therefore worth examining not as expected outcomes but as plausible worst cases. Eliminating RCP8.5/SSP5-8.5 therefore commits one of the cardinal sins of risk assessment: assuming the worst case will not occur. In addition, NCA5 frequently uses these scenarios in global-warming-level analysis, which evaluates impacts at different levels of warming but makes no claim about how likely any level of warming is. Overall, removing RCP8.5/SSP5-8.5 analyses would strip sound science from the assessment and make it harder for U.S. policymakers to evaluate the risks of climate change.

This study quantifies net savings to consumers and the economy in the wholesale electricity market attributable to grid-scale battery storage in ERCOT and CAISO. To do this, we reconstruct each market’s day-ahead supply curve for every hour of 2024–2025 directly from the price-quantity offers submitted by each generator, remove the battery fleet’s offers, and re-clear the market at the same demand. In ERCOT, batteries produced net consumer savings of $1.4 billion (95% CI $0.8–2.0 billion) in 2024 and $3.0 billion ($2.0–4.1 billion) in 2025; the estimate is positive under every assumption examined, and more than three-quarters of the gross savings is concentrated in the 1% of highest-saving hours — tight summer evenings when batteries kept the market from relying on the most expensive generators. In CAISO, the net effect was much smaller, +$123 million (95% CI +$3 to +$239 million) in 2024 and −$5 million (−$95 to +$92 million) in 2025. A second metric — production-cost savings — shows that batteries barely change what the ERCOT system costs to run ($92 million of savings in 2024, $281 million in 2025). The cost savings for ERCOT consumers therefore comes from transferring billions from generators to consumers. In CAISO batteries generate efficiency gains ($486 million and $651 million at the central estimate) that competition passes to low-cost generators rather than consumers. In both markets, batteries reshape who pays whom far more than they change what power costs to produce. These results suggest that storage procurement policy should evaluate ratepayer benefits by how much scarcity remains for storage to displace, not by installed capacity.

A July 2025 report from the U.S. Department of Energy (DOE) made the key claim that the stratosphere has warmed since 2000, contrary to model projections and inconsistent with the expected anthropogenic fingerprint. The DOE report provided no references or data to support this claim. Its basis appears to be an unpublished figure comparing simulated and observed tropical trends in the temperature of the lower stratosphere (TLS), a layer extending from roughly 15 to 20 km above Earth's surface. The observed tropical TLS trends shown in the unpublished DOE figure are incorrect. When the correct observational data sets are used, model tropical TLS trends are consistent with satellite observations, and a model‐predicted anthropogenic fingerprint is identifiable with high confidence in observed latitude‐altitude profiles of tropical temperature change. An earlier rebuttal of the DOE “no human fingerprint” claim considered global‐mean temperature changes only and did not perform a pattern‐based fingerprint study. Unless corrected or retracted, the DOE report will continue to misinform policymakers and the public about the reality of human effects on climate.

We built a 25-km record of smoke over the contiguous United States (CONUS) from MODIS MAIAC granules (MCD19A2.061) covering 2000–2025 and quantified the occurrence of wildfire smoke over this period. Smoke days over CONUS more than doubled from a mean of 3.07 per year in 2003–2013 to 6.99 in 2014–2024. The slope is +0.29 [95% CI: +0.04, +0.51] days/yr, with 48% of the record’s total smoke-day burden falling in its last five years. The smoke AOD index, which combines occurrence with optical depth, rises at 8.9%/yr. Breaking it down into frequency times intensity, 74% of the growth is smoke occurring more often with the remainder due to smoke being thicker. The increase is seasonally and spatially concentrated: 91% of it falls in July, August and September, with no detectable shift in the timing of the season. Compared against NOAA’s Hazard Mapping System heavy-smoke polygons over 2011–2024, an entirely independent product, the record agrees closely: r = 0.960 across 175 months, r = 0.946 annually, a median per-cell temporal correlation of 0.83, and a near one-to-one slope.

Different ways of counting heat‐related deaths (HRD) can give you very different numbers. This study examines HRD in Texas using three different definitions: The Optimal Temperature Method (OTM) estimates mortality based on deviations from a community's optimal temperature, capturing the effects of both moderate and extreme heat exposure. This method finds that 2.2% of summertime Texas mortality were heat related over the period 2010–2023. The Extreme Heat Method (XHM) counts deaths associated with extreme temperatures; we find that temperatures exceeding the 95th percentile were responsible for 0.5% of summertime Texas mortality over this same period. This means that moderate heat is responsible for 77% of HRD, with extreme temperatures responsible for the rest. The Excess Death Method (EDM) approach quantifies the mortality burden as the increase in mortality compared to what would have occurred with the climate of a baseline period; we find that summertime Texas mortality over this period was 1.7% higher than with the climate of the mid‐20th century. When comparing these estimates to official HRD values from the State of Texas, which are based on an official determination that heat contributed to the death, we find that official State HRD numbers appear to substantially underreport HRD, attributing just 0.3% of summertime deaths to heat, with the XHM method being the closest.

On behalf of the more than 85 experts who contributed to the Climate Experts’ Review of the DOE Climate Working Group Report, we are writing to submit this compendium of public comments on the Climate Working Group (CWG) Report entitled A Critical Review of Impacts of Greenhouse Gas Emissions on the U.S. Climate, under docket number DOE-HQ-2035-0207. This compendium begins with a Summary for Policy Makers that highlights a selection of key points from across the constituent Comments. It then contains 48 distinct Comments, each of which makes a variety of points regarding different elements of the CWG report and the report as a whole. Authorship of each Comment is separately noted. It concludes with biographical sketches providing the authors’ credentials. We hope the Summary for Policy Makers and the 48 Comments will be given full consideration and that, as with public comments on National Climate Assessments, there will be a substantive response to each and every element of these comments. As explained at length in these comments, the CWG report currently fails to adequately represent the scientific understanding of climate change. DOE must subject the CWG report to unbiased, robust, and transparent peer review under the Information Quality Act and other federal requirements. Accordingly, it will require very substantial revision before it can be relied upon by any federal agency or other entity.In response to the Department of Energy’s recent climate report, more than 85 scientists came together to submit a detailed rebuttal. Our motivation was simple: the DOE report misrepresents the state of climate science by cherry-picking evidence, exaggerating uncertainties, and ignoring decades of peer-reviewed research. Climate science is one of the most scrutinized and well-established fields, and the DOE report falls far short of that standard.

Different ways of counting heat-related deaths (HRD) can give you very different numbers. This study examines HRD in Texas using three different definitions: The Optimal Temperature Method (OTM) estimates mortality based on deviations from a community’s optimal temperature, capturing the effects of both moderate and extreme heat exposure. This method finds that 2.2% of summertime Texas mortality were heat related over the period 2010-2023. The Extreme Heat Method (XHM) only counts deaths associated with extreme temperatures; we find that temperatures exceeding the 95th percentile were responsible for 0.5% of summertime Texas mortality over this same period. This means that moderate heat is responsible for 77% of HRD, with extreme temperatures responsible for the rest. The Excess Death Method (EDM) approach quantifies the mortality burden as the increase in mortality compared to what would have occurred during a baseline period; we find that summertime Texas mortality over this period was 1.7% higher than a mid-20th century baseline. When comparing these estimates to official HRD values from the State of Texas, which are based on an official determination that heat contributed to the death, we find that official State HRD numbers appear to substantially underreport HRD, attributing just 0.3% of summertime deaths to heat, with the XHM method being the closest.

Global warming results from anthropogenic greenhouse gas emissions which upset the delicate balance between the incoming sunlight, and the reflected and emitted radiation from Earth. The imbalance leads to energy accumulation in the atmosphere, oceans and land, and melting of the cryosphere, resulting in increasing temperatures, rising sea levels, and more extreme weather around the globe. Despite the fundamental role of the energy imbalance in regulating the climate system, as known to humanity for more than two centuries, our capacity to observe it is rapidly deteriorating as satellites are being decommissioned.

This study focuses on the Electric Reliability Council of Texas (ERCOT) electricity market in Texas and demonstrates how the increase in temperature due to climate change is already driving large increases in electricity demand and total electricity costs. Results show that, compared to a 1950–80 baseline climate, electricity demand in 2023 was 1.9 GW (3.9%) higher because of the extreme temperatures of that year—climate change contributed 47% of this increase, with the rest coming from short-term climate variability. As demand increases, so does the price per unit of electricity, so consumers are hit double: They must buy more electricity, and each unit of electricity costs more. Using data from the wholesale market, we estimate that the total cost of electricity (the combination of higher demand and higher per unit prices) increased by $7.6B in 2023 compared to the baseline climate, $290 per ERCOT customer, with most of this increase occurring during the summer. Climate change contributed about 29% of this ($2.2B, $83 per customer), while short-term variability contributed the rest. About two-thirds of this increase is due to price increases triggered when the ERCOT grid becomes constrained. Investments in increasing the power supply or the ability to transmit it across the state, or reducing demand (e.g., demand response), could substantially reduce the impact of increasing temperature on the cost of electricity in Texas. Significance Statement: Quantifying the impacts of warmer temperatures due to climate change on society is a key goal of the climate science community. In this paper, we develop a methodology for calculating the cost of increased temperatures on electricity consumption. We show that climate change is driving up the costs of electricity in Texas. Compared to the climate of the mid-twentieth century, electricity demand was 4.1% higher in 2023, with climate change responsible for about half of this increase. This increased the total cost of electricity by $7.6 billion, $290 per person. Climate change contributed about 29% of this extra cost, representing a significant burden on the poorest in our society.