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U.S. Global Change Research Program Climate Science Special Report (Cssr), Donald Wuebbles, David Fahey, Kathleen A. Hibbard, D. J. Dokken, B. C. Stewart, T. K. Maycock

United States Department of Commerce: Staff Publications

Fifth-Order Draft

Table of Contents

Front Matter

About This Report........................................................................................ 1

Guide to the Report......................................................................................4

Executive Summary ................................................................................... 12

Chapters

1. Our Globally Changing Climate .......................................................... 38

2. Physical Drivers of Climate Change ................................................... 98

3. Detection and Attribution of Climate Change .................................... 160

4. Climate Models, Scenarios, and Projections .................................... 186

5. Large-Scale Circulation and Climate Variability ................................ 228

6. Temperature Changes in the United States ...................................... 267

7. Precipitation Change in the United States ......................................... 301

8. Droughts, Floods, and Hydrology ......................................................... 336

9. Extreme Storms ....................................................................................... 375

10. Changes in Land Cover and Terrestrial Biogeochemistry ............ 405 …

Tip-Enhanced Raman Scattering Of Graphene, Ryan Beams

United States Department of Commerce: Staff Publications

This article reviews the mechanism of tip-enhanced Raman spectroscopy (TERS) and its importance for characterizing graphene. The theoretical foundation of TERS and experimental implementation are discussed. Conventionally, Raman scattering is treated as a spatially incoherent process where the total signal is proportional to the scattering volume. However, in the near-field regime, the scattered fields can add coherently because the TERS interaction volume is on the same length scale as the phonon correlation length. These coherence effects are significant for two-dimensional materials as will be discussed theoretically and experimentally. Therefore, TERS provides an optical method to probe phonon correlations at the …

Emissions Of Glyoxal And Other Carbonyl Compounds From Agricultural Biomass Burning Plumes Sampled By Aircraft, Kyle J. Zarzana, Kyung-Eun Min, Rebecca A. Washenfelder, Jennifer Kaiser, Mitchell Krawiec-Thayer, Jeff Peischl, J. Andrew Neuman, John B. Nowak, Nicholas L. Wagner, William P. Dubè, Jason M. St. Clair, Glenn M. Wolfe, Thomas F. Hanisco, Frank N. Keutsch, Thomas B. Ryerson, Steven S. Brown

United States Department of Commerce: Staff Publications

We report enhancements of glyoxal and methylglyoxal relative to carbon monoxide and formaldehyde in agricultural biomass burning plumes intercepted by the NOAA WP-3D aircraft during the 2013 Southeast Nexus and 2015 Shale Oil and Natural Gas Nexus campaigns. Glyoxal and methylglyoxal were measured using broadband cavity enhanced spectroscopy, which for glyoxal provides a highly selective and sensitive measurement. While enhancement ratios of other species such as methane and formaldehyde were consistent with previous measurements, glyoxal enhancements relative to carbon monoxide averaged 0.0016 ± 0.0009, a factor of 4 lower than values used in global models. Glyoxal enhancements relative to formaldehyde …

Comparisons Of Airborne Measurements And Inventory Estimates Of Methane Emissions In The Alberta Upstream Oil And Gas Sector, Matthew R. Johnson, David R. Tyner, Stephen Conley, Stefan Schwietzke, Daniel Zavala-Araiza

United States Department of Commerce: Staff Publications

Airborne measurements of methane emissions from oil and gas infrastructure were completed over two regions of Alberta, Canada. These top-down measurements were directly compared with region-specific bottom-up inventories that utilized current industry-reported flaring and venting volumes (reported data) and quantitative estimates of unreported venting and fugitive sources. For the 50 × 50 km measurement region near Red Deer, characterized by natural gas and light oil production, measured methane fluxes were more than 17 times greater than that derived from directly reported data but consistent with our region-specific bottom-up inventory-based estimate. For the 60 × 60 km measurement region near Lloydminster, …

Acronyms And Units For Climate Science Special Report (Appendix D)

United States Department of Commerce: Staff Publications

Alphabetical list of Acronyms, Agencies, Abbreviations and Units used in the Report.

Multiple Method Analysis Of Tio2 Nanoparticle Uptake In Rice (Oryza Sativa L.) Plants, Yingqing Deng, Elijah J. Petersen, Katie E. Challis, Savelas A. Rabb, R. David Holbrook, James F. Ranville, Bryant C. Nelson, Baoshan Xing

United States Department of Commerce: Staff Publications

Understanding the translocation of nanoparticles (NPs) into plants is challenging because qualitative and quantitative methods are still being developed and the comparability of results among different methods is unclear. In this study, uptake of titanium dioxide NPs and larger bulk particles (BPs) in rice plant (Oryza sativa L.) tissues was evaluated using three orthogonal techniques: electron microscopy, single-particle inductively coupled plasma mass spectroscopy (spICP-MS) with two different plant digestion approaches, and total elemental analysis using ICP optical emission spectroscopy. In agreement with electron microscopy results, total elemental analysis of plants exposed to TiO₂ NPs and BPs at 5 …

Detection And Attribution Methodologies Overview (Appendix C), Thomas Knutson

United States Department of Commerce: Staff Publications

In this appendix, we present a brief overview of the methodologies and methodological issues for detection and attribution of climate change. Attributing an observed change or an event partly to a causal factor (such as anthropogenic climate forcing) normally requires that the change first be detectable (Hegerl et al. 2010). A detectable observed change is one which is determined to be highly unlikely to occur (less than about a 10% chance) due to internal variability alone, without necessarily being ascribed to a causal factor. An attributable change refers to a change in which the relative contribution of causal factors has …

Weighting Strategy For The Fourth National Climate Assessment (Appendix B), Benjamin Sanderson, Michael Wehner

United States Department of Commerce: Staff Publications

This document briefly describes a weighting strategy for use with the Climate Model Intercomparison Project, Phase 5 (CMIP5) multimodel archive in the 4th National Climate Assessment. This approach considers both skill in the climatological performance of models over North America and the interdependency of models arising from common parameterizations or tuning practices. The method exploits information relating to the climatological mean state of a number of projection-relevant variables as well as long-term metrics representing long-term statistics of weather extremes. The weights, once computed, can be used to simply compute weighted mean and significance information from an ensemble containing multiple initial …

Observational Datasets Used In Climate Studies (Appendix A), Donald Wuebbles

United States Department of Commerce: Staff Publications

Observations, including those from satellites, mobile platforms, field campaigns and ground based networks, provide the basis of knowledge on many temporal and spatial scales for understanding the changes occurring in Earth’s climate system. These observations also inform the development, calibration, and evaluation of numerical models of the physics, chemistry, and biology being used in analyzing the past changes in climate and for making future projections. As all observational data collected by support from Federal agencies are required to be made available free of charge with machine readable metadata, everyone can access these products for their personal analysis and research and …

Potential Surprises – Compound Extremes And Tipping Elements, Robert Kopp, David R. Easterling, Timothy Hall, Katharine Hayhoe, Radley Horton, Kenneth Kunkel, Allegra Legrande

United States Department of Commerce: Staff Publications

1. Positive feedbacks (self-reinforcing cycles) within the climate system have the potential to accelerate human-induced climate change and even shift the Earth’s climate system, in part or in whole, into new states that are very different from those experienced in the recent past (for example, ones with greatly diminished ice sheets or different large-scale patterns of atmosphere or ocean circulation). Some feedbacks and potential state shifts can be modeled and quantified; others can be modeled or identified but not quantified; and some are probably still unknown. (Very high confidence in the potential for state shifts and in the incompleteness …

Perspectives On Climate Change Mitigation, Benjamin Deangelo, James Edmonds, David Fahey, Benjamin Sanderson

United States Department of Commerce: Staff Publications

1. Warming and associated climate effects from CO2 3 emissions persist for decades to millennia. In the near-term, changes in climate are determined by past and present greenhouse gas emissions modified by natural variability. Reducing the total concentration of atmospheric CO2 is necessary to limit near-term climate change and stay below long-term warming targets (such as the oft-cited 3.6°F [2°C] goal). Other greenhouse gases (for example, methane) and black carbon aerosols exert stronger warming effects than CO2 on a per ton basis, but they do not persist as long in the atmosphere; therefore, mitigation of non-CO2 species contributes substantially to …

Ocean Changes – Warming, Stratification, Circulation, Acidification, And Deoxygenation, Libby Jewett, Anastasia Romanou

United States Department of Commerce: Staff Publications

1. The world’s oceans have absorbed about 93% of the excess heat caused by greenhouse gas warming since the mid-20th century, making them warmer and altering global and regional climate feedbacks. Ocean heat content has increased at all depths since the 1960s and surface waters have warmed by about 1.3° ± 0.1°F (0.7° ± 0.08°C) per century globally since 1900 to 2016. Under a high emissions scenario, a global increase in average sea surface temperature of 4.9° ± 1.3°F (2.7° ± 0.7°C) by 2100 is projected, with even higher changes in some U.S. coastal regions. (Very high confidence) …

Sea Level Rise, William Sweet, Radley Horton, Robert Kopp, Anastasia Romanou

United States Department of Commerce: Staff Publications

1. Global mean sea level (GMSL) has risen by about 7–8 inches (about 16–21 cm) since 1900, with about 3 of those inches (about 7 cm) occurring since 1993 (very high confidence). Human-caused climate change has made a substantial contribution to GMSL rise since 1900 (high confidence), contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years (medium confidence).

2. Relative to the year 2000, GMSL is very likely to rise by 0.3–0.6 feet (9–18 cm) by 2030, 0.5–1.2 feet (15–38 cm) by 2050, and …

Arctic Changes And Their Effects On Alaska And The Rest Of The United States, Patrick Taylor, Wieslaw Maslowski, Judith Perlwitz, Donald Wuebbles

United States Department of Commerce: Staff Publications

1. Annual average near-surface air temperatures across Alaska and the Arctic have increased over the last 50 years at a rate more than twice as fast as the global average temperature. (Very high confidence)

2. Rising Alaskan permafrost temperatures are causing permafrost to thaw and become more discontinuous; this process releases additional CO₂ and methane, resulting in an amplifying feedback and additional warming (high confidence). The overall magnitude of the permafrost–carbon feedback is uncertain; however, it is clear that these emissions have the potential to complicate the ability to meet policy goals for the reduction …

Changes In Land Cover And Terrestrial Biogeochemistry, Kathleen Hibbard, Forrest Hoffman, Deborah N. Huntzinger, Tristram West

United States Department of Commerce: Staff Publications

1. Changes in land use and land cover due to human activities produce physical changes in land surface albedo, latent and sensible heat, and atmospheric aerosol and greenhouse gas concentrations. The combined effects of these changes have recently been estimated to account for 40% ± 16% of the human-caused global radiative forcing from 1850 to present day (high confidence). As a whole, the terrestrial biosphere (soil and plants) is a net “sink” for carbon (drawing down carbon from the atmosphere), and this sink has steadily increased since 1980 (very high confidence). Because of the uncertainty in …

Extreme Storms, James Kossin, Timothy Hall, Thomas Knutson, Kenneth Kunkel, Robert Trapp, Duane Waliser, Michael Wehner

United States Department of Commerce: Staff Publications

1. Human activities have contributed substantially to observed ocean–atmosphere variability in the Atlantic Ocean (medium confidence), and these changes have contributed to the observed upward trend in North Atlantic hurricane activity since the 1970s (medium confidence).

2. Both theory and numerical modeling simulations (in general) indicate an increase in tropical cyclone (TC) intensity in a warmer world, and the models generally show an increase in the number of very intense TCs. For Atlantic and eastern North Pacific hurricanes and western North Pacific typhoons, increases are projected in precipitation rates (high confidence) and intensity (medium …

Droughts, Floods, And Hydrology, Michael Wehner, Jeff Arnold, Thomas Knutson, Kenneth Kunkel, Allegra Legrande

United States Department of Commerce: Staff Publications

1. Recent droughts and associated heat waves have reached record intensity in some regions of the United States; however, by geographical scale and duration, the Dust Bowl era of the 1930s remains the benchmark drought and extreme heat event in the historical record (very high confidence). While by some measures, drought has decreased over much of the continental United States in association with long-term increases in precipitation, neither the precipitation increases nor inferred drought decreases have been confidently attributed to anthropogenic forcing.

2. The human effect on recent major U.S. droughts is complicated. Little evidence is found for …

Precipitation Change In The United States, David R. Easterling, Jeff Arnold, Thomas Knutson, Kenneth Kunkel, Allegra Legrande, L. Ruby Leung, Russell Vose, Duane Waliser, Michael Wehner

United States Department of Commerce: Staff Publications

1. Annual precipitation has decreased in much of the West, Southwest, and Southeast and increased in most of the Northern and Southern Plains, Midwest, and Northeast. A national average increase of 4% in annual precipitation since 1901 is mostly a result of large increases in the fall season. (Medium confidence)

2. Heavy precipitation events in most parts of the United States have increased in both intensity and frequency since 1901 (high confidence). There are important regional differences in trends, with the largest increases occurring in the northeastern United States (high confidence). In particular, mesoscale …

Temperature Changes In The United States, Russell Vose, David R. Easterling, Kenneth Kunkel, Michael Wehner

United States Department of Commerce: Staff Publications

1. Average annual temperature over the contiguous United States has increased by 1.2°F (0.7°C) for the period 1986–2016 relative to 1901–1960 and by 1.8°F (1.0°C) based on a linear regression for the period 1895–2016 (very high confidence). Surface and satellite data are consistent in their depiction of rapid warming since 1979 (high confidence). Paleo-temperature evidence shows that recent decades are the warmest of the past 1,500 years (medium confidence).

2. There have been marked changes in temperature extremes across the contiguous United States. The frequency of cold waves has decreased since the early 1900s, and …

Large-Scale Circulation And Climate Variability, Judith Perlwitz, Thomas Knutson, James Kossin

United States Department of Commerce: Staff Publications

1. The tropics have expanded poleward by about 70 to 200 miles in each hemisphere over the period 1979-2009, with an accompanying shift of the subtropical dry zones, midlatitude jets, and storm tracks (medium to high confidence). Human activities have played a role in this change (medium confidence), although confidence is presently low regarding the magnitude of the human contribution relative to natural variability.

2. Recurring patterns of variability in large-scale atmospheric circulation (such as the North Atlantic Oscillation and Nordlem Annular Mode) and the atmosphere-ocean system (such as El Niño-Southern Oscillation) cause year-to-year variations in …

Climate Models, Scenarios, And Projections, Katharine Hayhoe, James Edmonds, Robert Kopp, Allegra Legrande, Benjamin Sanderson, Michael Wehner, Donald Wuebbles

United States Department of Commerce: Staff Publications

1. If greenhouse gas concentrations were stabilized at their current level, existing concentrations would commit the world to at least an additional 1.1°F (0.6°C) of warming over this century relative to the last few decades (high confidence in continued warming, medium confidence in amount of warming).

2. Over the next two decades, global temperature increase is projected to be between 0.5°F and 1.3°F (0.3°–0.7°C) (medium confidence). This range is primarily due to uncertainties in natural sources of variability that affect short-term trends. In some regions, this means that the trend may not be distinguishable from natural variability ( …

Detection And Attribution Of Climate Change, Thomas Knutson, James Kossin, Carl Mears, Judith Perlwitz, Michael Wehner

United States Department of Commerce: Staff Publications

1. The likely range of the human contribution to the global mean temperature increase over the period 1951–2010 is 1.1° to 1.4°F (0.6° to 0.8°C), and the central estimate of the observed warming of 1.2°F (0.65°C) lies within this range (high confidence). This translates to a likely human contribution of 93%–123% of the observed 1951–2010 change. It is extremely likely that more than half of the global mean temperature increase since 1951 was caused by human influence on climate (high confidence). The likely contributions of natural forcing and internal variability to global temperature change over that …

Physical Drivers Of Climate Change, David Fahey, Sarah Doherty, Kathleen A. Hibbard, Anastasia Romanou, Patrick Taylor

United States Department of Commerce: Staff Publications

1. Human activities continue to significantly affect Earth’s climate by altering factors that change its radiative balance. These factors, known as radiative forcings, include changes in greenhouse gases, small airborne particles (aerosols), and the reflectivity of the Earth’s surface. In the industrial era, human activities have been, and are increasingly, the dominant cause of climate warming. The increase in radiative forcing due to these activities has far exceeded the relatively small net increase due to natural factors, which include changes in energy from the sun and the cooling effect of volcanic eruptions. (Very high confidence)

2. Aerosols caused …