US Climate Science Special Report

Highlights of the Findings of the U.S. Global Change Research Program Climate Science Special Report:


The climate of the United States is strongly connected to the changing global climate. The statements below highlight past, current, and projected climate changes for the United States and the globe.

Global annually averaged surface air temperature has increased by about 1.8°F (1.0°C) over the last 115 years (1901–2016). This period is now the warmest in the history of modern civilization. The last few years have also seen record-breaking, climate-related weather extremes, and the last three years have been the warmest years on record for the globe. These trends are expected to continue over climate timescales.

This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.

In addition to warming, many other aspects of global climate are changing, primarily in response to human activities. Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and increasing atmospheric water vapor.

For example, global average sea level has risen by about 7–8 inches since 1900, with almost half (about 3 inches) of that rise occurring since 1993. Human-caused climate change has made a substantial contribution to this rise since 1900, contributing to a rate of rise that is greater than during any preceding century in at least 2,800 years. Global sea level rise has already affected the United States; the incidence of daily tidal flooding is accelerating in more than 25 Atlantic and Gulf Coast cities.

Global average sea levels are expected to continue to rise—by at least several inches in the next 15 years and by 1–4 feet by 2100. A rise of as much as 8 feet by 2100 cannot be ruled out. Sea level rise will be higher than the global average on the East and Gulf Coasts of the United States.

Changes in the characteristics of extreme events are particularly important for human safety, infrastructure, agriculture, water quality and quantity, and natural ecosystems. Heavy rainfall is increasing in intensity and frequency across the United States and globally and is expected to continue to increase. The largest observed changes in the United States have occurred in the Northeast.

Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent. Recent record-setting hot years are projected to become common in the near future for the United States, as annual average temperatures continue to rise. Annual average temperature over the contiguous United States has increased by 1.8°F (1.0°C) for the period 1901–2016; over the next few decades (2021–2050), annual average temperatures are expected to rise by about 2.5°F for the United States, relative to the recent past (average from 1976–2005), under all plausible future climate scenarios.

The incidence of large forest fires in the western United States and Alaska has increased since the early 1980s and is projected to further increase in those regions as the climate changes, with profound changes to regional ecosystems.

Annual trends toward earlier spring melt and reduced snowpack are already affecting water resources in the western United States and these trends are expected to continue. Under higher scenarios, and assuming no change to current water resources management, chronic, long-durationhydrological drought is increasingly possible before the end of this century.

The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without major reductions in emissions, the increase in annual average global temperature relative to preindustrial times could reach 9°F (5°C) or more by the end of this century. With significant reductions in emissions, the increase in annual average global temperature could be limited to 3.6°F (2°C) or less.

The global atmospheric carbon dioxide (CO2) concentration has now passed 400 parts per million (ppm), a level that last occurred about 3 million years ago, when both global average temperature and sea level were significantly higher than today. Continued growth in CO2 emissions over this century and beyond would lead to an atmospheric concentration not experienced in tens to hundreds of millions of years. There is broad consensus that the further and the faster the Earth system is pushed towards warming, the greater the risk of unanticipated changes and impacts, some of which are potentially large and irreversible.

The observed increase in carbon emissions over the past 15–20 years has been consistent with higher emissions pathways. In 2014 and 2015, emission growth rates slowed as economic growth became less carbon-intensive. Even if this slowing trend continues, however, it is not yet at a rate that would limit global average temperature change to well below 3.6°F (2°C) above preindustrial levels.

A Summary of Advances Since NCA3

Advances in scientific understanding and scientific approach, as well as developments in global policy, have occurred since NCA3. A detailed summary of these advances can be found at the end of Chapter 1: Our Globally Changing Climate. Highlights of what aspects are either especially strengthened or are emerging in the current findings include

  • Detection and attribution: Significant advances have been made in the attribution of the human influence for individual climate and weather extreme events since NCA3. (Ch. 3678).
  • Atmospheric circulation and extreme events: The extent to which atmospheric circulation in the midlatitudes is changing or is projected to change, possibly in ways not captured by current climate models, is a new important area of research. (Ch. 567).
  • Increased understanding of specific types of extreme events: How climate change may affect specific types of extreme events in the United States is another key area where scientific understanding has advanced. (Chapter 9).
  • High-resolution global climate model simulations: As computing resources have grown, multidecadal simulations of global climate models are now being conducted at horizontal resolutions on the order of 15 miles (25 km) that provide more realistic characterization of intense weather systems, including hurricanes. (Chapter 9).
  • Oceans and coastal waters: Ocean acidification, warming, and oxygen loss are all increasing, and scientific understanding of the severity of their impacts is growing. Both oxygen loss and acidification may be magnified in some U.S. coastal waters relative to the global average, raising the risk of serious ecological and economic consequences. (Chapters 213).
  • Local sea level change projections: For the first time in the NCA process, sea level rise projections incorporate geographic variation based on factors such as local land subsidence, ocean currents, and changes in Earth’s gravitational field. (Chapter 12).
  • Accelerated ice-sheet loss: New observations from many different sources confirm that ice-sheet loss is accelerating. Combining observations with simultaneous advances in the physical understanding of ice sheets leads to the conclusion that up to 8.5 feet of global sea level rise is possible by 2100 under a higher scenario (RCP8.5), up from 6.6 feet in NCA3. (Chapter 12).
  • Low sea-ice areal extent: The annual arctic sea ice extent minimum for 2016 relative to the long-term record was the second lowest on record. The arctic sea ice minimums in 2014 and 2015 were also amongst the lowest on record. Since 1981, the sea ice minimum has decreased by 13.3% per decade, more than 46% over the 35 years. The annual arctic sea ice maximum in March 2017 was the lowest maximum areal extent on record. (Chapter 11).
  • Potential surprises: Both large-scale state shifts in the climate system (sometimes called “tipping points”) and compound extremes have the potential to generate unanticipated climate surprises. The further the Earth system departs from historical climate forcings, and the more the climate changes, the greater the potential for these surprises. (Chapter 15).
  • Mitigation: This report discusses some important aspects of climate science that are relevant to long-term temperature goals and different mitigation scenarios, including those implied by government announcements for the Paris Agreement. (Chapters 414).

Executive Summary

https://science2017.globalchange.gov/

24 Comments

  1. chrism56

     /  November 4, 2017

    The report is known for cherrypicking data – here is a redteam critique of the chapter von sea level rise showing how it disregards inconvenience evidence.
    https://curryja.files.wordpress.com/2017/11/cssr-on-slr.pdf

    • Mefrostate

       /  November 4, 2017

      Am I missing something? He claims that the CSSR report “fails to mention the fluctuations” in GMSL. But his own report contains a quote where the fluctuations are mentioned “In addition to the overall increase in the rate of sea-level rise, there is also considerable variability in the rate”.

      Although I guess it’s unsurprising that he made that mistake, given his critique was released before the CSSR report was published

      • Alan Wilkinson

         /  November 4, 2017

        First line said: In discussing global sea level rise since 1900, the draft Climate Science Special Report (CSSR

        The quote you mentioned re variability is in the cited work, not in the CSSSR. His complaint is that the CSSR selectively and misleadingly reported.

        Neither of your snarks are valid.

        • Mefrostate

           /  November 4, 2017

          Right, fair point about the draft.

          And reading from that draft:

          Compared to many climate variables, the trend signal for sea level change tends to be large relative to natural variability. However, at interannual timescales, changes in ocean dynamics, density, and wind can cause substantial sea level variability in some regions.

          I note that the chapter goes on to explore the wide range of factors contributing to variation in sea levels over time and space, and unpicks the underlying trends with which we should be concerned.

          Koonin’s critique is an excellent rhetorical trick for casting doubt at the CSSR into the public discussion, and is particularly easy to absorb for those predisposed & desirous of downplaying the potential effects of anthropogenic climate change. Chrism56 calls these people the “redteam” although I wouldn’t be quite as nasty.

          • chrism56

             /  November 5, 2017

            red team is the accepted term done for those that are specifically assembled to pick holes in a case put forward – originally military, but now a lot wider application. Even lawyers do it – god forbid.
            https://en.wikipedia.org/wiki/Red_team
            And why is Koonin’s analysis a rhetorical trick – could it be that he caught out the authors modifying the science into advocacy because they deliberately left out the major qualifications?

          • Alan Wilkinson

             /  November 5, 2017

            The quote you resurrected has nothing to do with the critique that decadal trend patterns vary significantly and the CSSR lies by omission in selectively choosing one that suits its purpose.

    • Griff

       /  November 5, 2017

      Sea leval rate data church and white from a post at open mind
      https://tamino.wordpress.com/2017/07/25/sea-level-rise-has-accelerated/
      I don’t see Koonin the same as early rate.
      Probably because he uses 18 year smoothing so fudges the increasing trend in recent data .

      • chrism56

         /  November 5, 2017

        If you want to be so silly enough to post something from Mr Foster, Griff, you destroyed your credibility straight away. That graph was made by joining the satellite data to the tidal data with the paste point at 1993. They measured two different things. The satellites measured an extra ~1mm/ a year that was the isostacy component. That “acceleration” is not shown on tidal data. Go on to the NOAA website and look at it for long series like Battery Point or Fort Dennison.
        Church and White was a 2011 paper. Jevrejeva is the more recent one and has quite a different endpoint data.

      • chrism56

         /  November 5, 2017

        And Griff, it would help if you actually read the reports before mouthing off. Koonin didn’t use18 year smoothing to fudge things. The IPCC AR5 did the smoothing, and Koonin followed to keep the data compatable.
        If he had used the latest satellite data, it shows global sea level has dropped over the last year or so.

        • Griff

           /  November 5, 2017

          Two forms of data ?
          Very little difference between satellite and and tide data my friend .
          httpTs://tamino.files.wordpress.com/2017/07/both.jpg
          sea level has drooped ,,,,,face palm

          • Griff

             /  November 5, 2017

            Fudged the link
            here

          • chrism56

             /  November 5, 2017

            Believe it or not Griff, it is now 2017. Your graph stops at 2014. Here is the university of Colorado’s graph showing sea level until Aug 2016 showing it dropping.
            http://sealevel.colorado.edu/files/2016_rel4/sl_ns_global.pdf
            Now, where did you say you put your credibility because it seems to be lost?
            And quoting from the abstract of Jevrevera 2014, an author who IPCC AR5 used as one of their main sources on sea level.
            “The new reconstruction suggests a liner trend of 1.9±0.3mm/yr during the 20th Century, with 1.8±0.5mm/yr since 1970.

            • Griff

               /  November 6, 2017

              ROFL
              ” abstract of Jevrevera 2014″
              They dont do time travel my friend your date is after the 31 /7 /12 cut of point for acceptance of papers in ar5 wg1.
              Its Jevrevera 2008 they use .Cherry picking one paper that supports your spin and ignoring the rest is a familiar pattern to me.
              Here is a discussion on real climate that includes a critique of the method used in Jevrevera 2008
              http://www.realclimate.org/index.php/archives/2013/01/sea-level-rise-where-we-stand-at-the-start-of-2013/
              See the first sea level graph! looking at the fluctuations not the trend is what we expect from a certain sort of ….
              Here is timino again using the latest nasa data.

            • chrism56

               /  November 6, 2017

              The CSSR deliberately cherrypicked the data they wanted to tell the story they wanted. That is why they truncated the satellite data and wouldn’t quote Ms Jervrejeva’s paper, even though it was the most recent peer reviewed document (speaking of peer review, why does Griff always link to partisan blog posts, rather than peer reviwed papers or even the data itself? Could it be that he can’t understand unless it is explained to him? )
              Sea level rise is only about 1.8mm/year and has been unchanged for over a century. I don’t even need to quote peer reviewed papers. The NOAA does the data averaging for me
              https://tidesandcurrents.noaa.gov/sltrends/slrmap.htm.
              The isostasy correction is irrelevant for flooding. What matters is where the sea level is relative to existing infrastructure, ie the tidal data. The data from the NZ ports is close to the worldwide average. They don’t have Port Chalmers for the flooding in St Kilda but Bluff is a bit below the average
              https://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.htm?stnid=690-041
              Even Kiribati, where they claim the situation is “dire” and they need to be climate refugees has had less than 40mm rise in 60 years https://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.htm?stnid=750-012
              And no sign of acceleration since 1993.
              When Griff can explain in his own words why the sea level rise acceleration isn’t present in ling term records like The Battery
              https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8518750
              or Fort Denison
              https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?stnid=8518750
              then he might have some credibility. Until then, he is just noise.

            • chrism56

               /  November 6, 2017

              The CSSR deliberately cherrypicked the data they wanted to tell the story they wanted. That is why they truncated the satellite data and wouldn’t quote Ms Jervrejeva’s paper, even though it was the most recent peer reviewed document (speaking of peer review, why does Griff always link to partisan blog posts, rather than peer reviwed papers or even the data itself? Could it be that he can’t understand unless it is explained to him? )
              Sea level rise is only about 1.8mm/year and has been unchanged for over a century. I don’t even need to quote peer reviewed papers. The NOAA does the data averaging for me
              https://tidesandcurrents.noaa.gov/sltrends/slrmap.htm.
              The isostasy correction is irrelevant for flooding. What matters is where the sea level is relative to existing infrastructure, ie the tidal data. The data from the NZ ports is close to the worldwide average. They don’t have Port Chalmers for the flooding in St Kilda but Bluff is a bit below the average
              https://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.htm?stnid=690-041
              Even Kiribati, where they claim the situation is “dire” and they need to be climate refugees has had less than 40mm rise in 60 years https://tidesandcurrents.noaa.gov/sltrends/sltrends_global_station.htm?stnid=750-012
              And no sign of acceleration since 1993.
              When Griff can explain in his own words why the sea level rise acceleration isn’t present in long term records like The Battery or Fort Denison, then he might have some credibility. Until then, he is just noise.

            • chrism56

               /  November 6, 2017

              Sorry about the double post – I saw my comment was in moderation, probably because I had too many links. In the time I had edited it removing some links, PG had allowed it through.

      • DaveK

         /  November 5, 2017

        Ha Tamino…good one, maybe I could trump that with a Willis Eisenbach perhaps? Nah, how about we leave pseudoscientists out of it and try something closer to home which shows exactly nil justification for NZ issuing special visas for all those poor pacific peoples fleeing the terror of rising seas.

        http://www.bom.gov.au/pacific/projects/pslm/index.shtml

        Sure, lots of the pacific has all sorts of environmental issues but rising sea levels isn’t one of them.

        • Griff

           /  November 6, 2017

          Timino is a statistician who has published well cited papers on climate change .
          Attacking the man not the data my friend .

          As to your link
          What is your point? Raw data is not a examination of sea level trend over time.
          We know globally sea level rate of rise is accelerating. Water is a fluid it will result in rise over the entire world .

  2. “This assessment concludes, based on extensive evidence, that it is extremely likely that human activities , especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.”
    I’ve made bold several points in case the ideologically blind and deaf commenters here who still deny, might have a chance to grasp the situation.

    • Blazer

       /  November 4, 2017

      Hardly earth shattering news Robert.Thought it was obvious to anyone that ‘human activities’ impacted on the environment.Concrete,glass,steel…it all comes from the earth.

      • robertguyton

         /  November 4, 2017

        “especially emissions of greenhouse gases”

  3. Maggy Wassilieff

     /  November 4, 2017

    The assessments are still based on dodgy climate models, met. stations suffering from UHI, and lousy data manipulations.
    https://wattsupwiththat.com/2017/11/03/what-you-wont-find-in-the-new-national-climate-assessment/

    http://www.climatedepot.com/2017/11/03/steven-koonin-a-deceptive-new-report-on-climate/

    • Griff

       /  November 5, 2017

      Yess maggy
      Except the result of uhi has been allowed for in the adjustments they make to insure the record is as accurate as possible.

      The satellite record confirms the robustness of the surface record
      1980 to present
      RSSv4.0 TLT Trend: 0.188 ±0.066 °C/decade (2σ)
      Berkeley global Trend: 0.185 ±0.038 °C/decade (2σ)

      Berkeley was initiated after claims that the temperatures were effected by UHF by your sources. Berkeley earth started from scratch ande developed independent methods to remove UHI effects.
      WUWT and others still refuse to accept the result.

  1. Climate Change 2017 Report – EDU HELP 101