Presentation on theme: "A World Of Change: Climate Yesterday, Today, and Tomorrow Susan Solomon Senior Scientist, NOAA, Boulder and ex-co chair IPCC WG1 IPCC, post-IPCC, irreversibility,"— Presentation transcript:
A World Of Change: Climate Yesterday, Today, and Tomorrow Susan Solomon Senior Scientist, NOAA, Boulder and ex-co chair IPCC WG1 IPCC, post-IPCC, irreversibility, and other key aspects of what we know about climate change
The World Has Warmed 2008: 10th warmest Widespread warming has occurred. Globally averaged, the planet is about 0.75°C warmer than it was in 1860, based upon dozens of high-quality long records using thermometers worldwide, including land and ocean. IPCC WG1 (2007)
Ups and downs from year to year? Yes, true. Relevant? No. 1997-2008 Global Average Climate Change 1977-1989 1987-1996 See Easterling et al., GRL, 2009
Our lives are heavily influenced by local weather. It’s important to distinguish between weather and climate. Fronts move air from one region to another (e.g., winter cold fronts) and cause large local variability. Averaging over space and/or time is critical to deducing meaningful climate changes.
Local And Global Changes (from NCDC data) Australia Global Average Fewer cold extremes http://www.ncdc.noaa. gov/gcag/index.jsp Canada China Near Denver, CO Near Paris
Rising atmospheric temperature Rising sea level Reduction in NH snow cover And…… Atmospheric water vapor increasing Glaciers retreating Arctic sea ice extent decreasing Extreme temperatures increasing …………. Warming is Unequivocal Many Changes Signal A Warming World IPCC WG1 (2007)
CARBON DIOXIDE A critical greenhouse gas Dramatic increase in industrial era, ‘forcing’ climate change Higher concentration than for more than 600,000 years Human Drivers of Climate Change: Unprecedented IPCC WG1 (2007)
Carbon Dioxide at Mauna Loa The biosphere ‘breathes’ every year in its growing cycle, but the human trend is clear. http://www.esrl.noaa.gov/gmd/ccgg/trends/ Big natural fluxes? Yes. Relevant? No
Global-average Radiative Forcing (RF) (W m -2 ) Forcing of Climate Change [1750 to Present-day] CO2 is largest Solar brightness effect small Carbon dioxide is causing the bulk of the forcing, and it lives a long time in our atmosphere (some of it lives for more than 1000 years). Every year of emission means a commitment to climate change for more than 30 generations. IPCC WG1 (2007)
Agung Chichon Pinatubo Observations Are Humans Responsible? IPCC (1995): “Balance of evidence suggests discernible human influence” IPCC (2001): “Most of global warming of past 50 years likely (odds 2 out of 3) due to human activities” IPCC (2007): “Most of global warming of past 50 years very likely (odds 9 out of 10) due to human increases in greenhouse gases” Natural forcings only Natural and human effects IPCC WG1 (2007) ch 9 and summary Volcanoes: proof of principle that forcing changes climate. GHG increases dominate forcing and climate changes of past 50 years.
Why can we say it’s very likely (90% odds) that most of the warming is due to increased greenhouse gases? High statistical confidence based on multiple fingerprints in time and space. Are Humans Responsible? IPCC WG1 (2007) ch 9 & summary
The Pine Beetle Perfect Storm Photo http://www.for.gov.bc.ca Reduced moisture, trees stressed; esp. lodgepole pine Longer beetle breeding season (two cycles, not one) Fewer extreme cold snaps to kill beetle in winter (below -20°F) Photo by Ken Papaleo / The Rocky Mountain News See, recent papers by Kurz et al in Nature and Mantgen et al in Science.
A different climate on each continent by 2050 IPCC WG1 (2007) ch 11 A changing world for everyone, including science and scientists. What about smaller scales?
A World of Change: More Rain for Some, Less for Others Regional changes (+/-) of up to 20% in average rainfall. At mid to low latitudes, dry get drier, wet get wetter. Dust bowl and other major droughts of the past: 5- 15% less rain over 10-20 yrs. DJF seasonal precipitation (2090s: medium emissions scenario; highest confidence in stippled areas) IPCC WG1 (2007) SPM
A World of Change: Less Rain for Some, More for Others Dry regions in the “subtropics”, wet regions at higher latitudes; basic pattern is linked to fundamental physics
UNFCCC and Science High confidence, well quantified information: Very useful. This part of the talk: irreversible changes that can be expected with high scientific confidence. observed changes are already occurring, and there is evidence for anthropogenic contributions to these changes the phenomenon is based upon physical principles thought to be well-understood projections are broadly robust across available models [“Geoengineering” to remove carbon or artificially cool not considered here.]
EMICs: New Tool to Probe the Very Long Term IPCC, WG1 (2007), chapter 10 UNFCCC Article 2: Stabilization of GHG at a level that avoids ‘dangerous interference’. Article 3: emphasizes “serious or irreversible damage” Beyond the 21st Century
Stop Emissions Completely: Can The World Return to A Natural State? IPCC, WG1 (2007), chapter 10 One test: ramp towards 750 stabilization, then stop. ≈450 ppmv left in 3000 Warming remains constant ±0.5°C for more than a thousand years.
Carbon Cycle: It Really Is A Cycle Some man- made CO2 goes (in the short-term) from the atmosphere to vegetation, surface ocean. Long term sink is deep ocean. It’s very slow.
Carbon Dioxide Is A Unique Gas: Multiple Timescales (1) CO 2 + H 2 O H + + HCO 3 - (2) CO 2 + H 2 O + CO 3 -2 2HCO 3 - CO 2 dissolves in seawater to acidify the ocean (1). Dissolution is limited by buffering. Added carbonate (eg rock weathering) can very slowly dissolve more (2). Initial step ~100,000 years Archer (many papers); review in Solomon et al., PNAS, 2009
Carbon Cycle: Back to Basics (Revelle and Suess, 1957) Isotopes: ocean sink and speed Long-term: 20% of human Gts input retained (Revelle factor)
Carbon Cycle: Gts And ppmv Half of human CO2 emissions (Gts) retained in atmosphere each year (airborne fraction or ‘instantaneous Revelle factor’). Long-term human CO2 Gts retained will be 20%, due to well understood processes in the ocean (Revelle factor). Long-term concentration retained will be 0.2/0.5, or about 0.4 of the peak concentration enhancement above pre-industrial value of 278 ppmv. Solomon et al., PNAS, 2009
Carbon Sink and Heat Transport: Links to Deep Ocean Linked physics and relationship to timescales for carbon and climate system inertia (also SLR due to thermal expansion).
Carbon Sink, Heat Transport, Climate Change, and Sea Level Rise Due to Thermal Expansion Broad range of test cases: Every year of climate change that occurs (warming, precip, snow cover, sea ice retreat, ocean acidification, etc…) due to carbon dioxide increases is irreversible for at least 1000 years. Sea level rise is slower, but is irreversibly linked to the peak CO2 we reach. Solomon et al., PNAS, 2009
Irreversible Precipitation Changes 5 to 10% per degree of warming in e.g., Southern Europe, North Africa, Western Australia, SW North America, South Africa in the respective dry seasons. ≈Forever. Compare to ‘dust bowl’ or other major droughts, typically 5-15% over ≈10-20 years. White: fewer than 2/3 of the models agree; colors and gray >2/3 Solomon et al., PNAS, 2009
Precipitation Change: How Far Will We Go? Best estimate of 21st century choices. The longer we wait to act, the more rainfall change we will be locked into. Solomon et al, PNAS, 2009
Irreversible Sea Level Rise: How Far Will We Go? add glaciers (0.2-0.7m) add ice sheets? Thermal expansion only: 0.2-0.6 m/°C Locked in during 21 st century Solomon et al., PNAS, 2009
Add Ice Sheets? How Quickly Do They Melt? Charbit et al., GRL, 2008 Can ice sheets outlast the carbon for some levels of perturbation? How much?
Sea level rise of 0.5-1.0 meter would have large impacts in many parts of the world. [From IPCC WG2 (2001).]
Carbon Dioxide Emission From Fossil Fuel Burning Who? Source: Energy Information Agency, DOE Us
Why: Going, Doing, Making, Being Comfortable….. In short, just about everything.
Carbon Dioxide Emission From Fossil Fuel Burning 5.5 B people now in the developing world emit about 5x less fossil CO 2 per person than the 1B in the developed world
Changes in Total and Per Capita Emissions of Carbon Dioxide From Fossil Fuel Burning in China and the USA Source: Energy Information Agency, DOE Last decade: China is getting richer, and emitting more CO 2 Kyoto Protocol?
Stabilization of CO 2 would require 50% emissions reductions (for a few decades) and then 80% Geoengineering? Cool the planet? Real and ‘artificial’ trees? Climate And Bathtubs: A Poorly-Understood Principle 5/6 of the people now emit 5x less per person than 1/6
How Far Will We Go? The longer we wait to act, the more climate change we will be locked into. Image: Socolow and Pacala
Some Possible Future Choices: Just Illustrations There are no silver bullets but there is much silver buckshot. Technology matters. 60 mpg cars Double current capacity 50x wind or 700x current solar Reduce deforestation Successful tests completed
Some Things I Hope You’ll Remember About Climate Change -Caused mainly by different long-lived gases produced by people via a well understood physical mechanism. CO 2 from fossil fuel burning is (by far) the main climate change agent. -Abundant data for at least a century, carefully calibrated, show the changes in the industrial era. -Temperatures are rising globally. There is local variability. -Young people today will live in a world some 5-10°F warmer by the time they are old men and women, if emissions continue ramping. -Rainfall changes with climate change would affect many people and ecosystems. Droughts like the dust bowl would be widespread. -Climate changes from CO2 emissions should be expected to last more than 1000 years (unless we find a ‘miracle cure’ to remove CO2) -Climate change challenges us to think beyond our own backyards.
22 AR4 models Regional averages over the respective dry seasons (not JJA, DJF, etc.), relative to 1900-1950 baseline Future changes dominated by GHG in these runs Rainfall Changes with Warming Solomon et al., PNAS, 2009
Uncertainty, Risk, and Confidence Structures Toxicology, epidemiology Greenland ice sheet? Climate change: A mix of things we now know quite well, and other things that represent high-impact but highly uncertain risks. Do more to identify what is well known…..separate from the much more uncertain risks to aid clarity and consensus. Stock markets?
How Accurate Are Model Simulations of Rainfall? Observed annual average precipitation (cm/year), 1980-1999; CMAP climatology Multi-model average IPCC WG1 (2007), chapter 8
The World Is Still Warm (post-IPCC 2007) Short-term variations (e.g., volcanoes, El Nino/La Nina in some years) don’t change the global ‘big picture.’ La Nina From www.realclimate.org
Some Key Underpinnings: Held and Soden; Seidel et al Change in obs bigger than models…. expansion of tropics mean rainfall trends heavy rain
Carbon Sink, Heat Transport, Climate Change, and Sea Level Rise Due to Thermal Expansion Broad range of test cases: Every year of climate change that occurs (warming, precip, snow cover, sea ice retreat, ocean acidification, etc…) due to carbon dioxide increases is irreversible for at least 1000 years. Sea level rise is slower, but is also irreversibly linked to the peak CO2 we reach. Solomon et al., PNAS, 2009
“Realized” Warming Actual and equilibrium temperatures, relative to CO2 change. During the period of CO2 rise, the realized warming fraction is about 50-60% of the climate sensitivity. After emissions stop, warming remains 50±10% of that for equilibrium relative to CO2 peak value. Solomon et al., PNAS, 2009