planetis&warming& global&environmental&change&user · 2013-12-10 · 2 10,000...
TRANSCRIPT
1
Global Environmental Change
What are things to watch and how will vegeta7on change
Planet is warming
Solar ac7vity and global temperatures are not in sink
Issue of global origin Basis of climate change
Basis of climate change
• Human changes that increase CO2 into the atmosphere or other greenhouse gasses. – Burning of fossil fuels (net gain) – Burning of vegeta7on (global issue) – Disturbance of natural communi7es (major increases in decomposi7on = net CO2 increase)
• Greenhouse gasses increase global average temperatures
Fossil Fuel Emission
(Gigaton
s C/yr) Increases greenhouse gasses
2
10,000 year record indicates CO2 increases associated with recent period.
A 400,000 year record suggests variation in CO2, but less than current levels.
LAND USE CHANGES, e.g., cutting down forests for agriculture, paving over vegetation, converting agriculture to suburbs or towns, greatly increase CO2 emissions. Anyplace with population growth or other development pressures (like forestry for other places) accelerate emissions.
Consider the balance between production and decomposition following disturbances.
Greenhouse Effect: How does it Work?
• Energy arrives from the sun at high energy wavelengths (UV, light) and leaves at lower energy wavelengths (IR heat).
• CO2 is ‘clear’ to higher energy wavelengths but opaque in the IR; heat is trapped in the atmosphere
Greenhouse Effect Overwarming
3
These graphs show the differences for years since 1850 compared to the 1961-1990 average
Planet is warming
Copenhagen Summary Report 2009
Changes global average air temperature (rela7ve to 1990)
-‐IPCC projec7ons
Days and nights are warming
Cool colors- decrease in frequency
Warm colors- increase in frequency
See bar graphs
For example, Marmots are emerging from hibernation on average 23 days earlier than 23 years ago. This coincides with an increase in average May temperatures of about 1.8°F (1°C) over the same time period.
Inouye et al. 2000. PNAS USA 97: 1630-‐1633.
Animal behavior and plant ranges are shifting.
Real problem is Phenology
• Disjunc7ons in the 7ming of plant and animal ac7vity (pollina7on and dispersal for plants; food resources for animals)
Temperature increases on plant communi7es
Recall that plant enzymes, like those in photosynthesis, operate optimally in a limited range of temperatures. At either extreme, rates of respiration can exceed photosynthesis.
Shifts to warmer temperatures will cause major shifts in plant communities.
4
Tropical Trees are slowing in growth rates
Varia7on in Annual Growth in Tropical Trees Measured by Diameter Growth of trunks.
Problem? The lack of growth is all recent…
…and it correlates directly with increasing CO2 flux (addi7ons to atmosphere)
Tropical Tree Growth is restrained by higher daily
minimum temperature (night 7me).
Tropics: Not going to be a carbon sink
Huge increases in CO2 addi7ons to the atmosphere under both ‘baseline’ (current rates) or ‘reduced PS’ scenarios.
Note that the tropics were hoped to be a major carbon sink, but these data force a re-evaluation from sink to neutral, or even a carbon source if warming trends continue.
Figure 3 | Changes in the Qori Kalis Glacier, Quelccaya Ice Cap, Peru, between 1978 (a) and 2002 (b). Glacier retreat during this time was 1,100m (L. Thompson, personal communication). Photographs courtesy of L. Thompson.
Glaciers are melting.
5
"On the left is a photograph of Muir Glacier taken on August 13, 1941, by glaciologist William O. Field; on the right, a photograph taken from the same vantage on August 31, 2004, by geologist Bruce F. Molnia of the United States Geological Survey (USGS)." Image credit: National Snow and Ice Data Center,
W. O. Field, B. F. Molnia.
Greenland’s ice sheet melts more and more each year.
Melt water flows into a large moulin in the Greenland ice sheet. Image credit: Roger J. Braithwaite, The University of Manchester, UK. Image Source: NASA.
Permafrost covers a massive amount of the northern hemisphere. Decomposition from thawed areas will release large amounts of ‘stored’ organic CO2.
Projected loss of both permafrost and sea ice in the arctic regions.
• Permafrost thawing. Permafrost thawing is causing the ground to subside 16-33 ft (4.9-10 m) in parts of interior Alaska. The permafrost surface has warmed by about 3.5oF (1.9oC) since the 1960's.
Osterkamp and Romanovsky. 1998. Permafrost and Periglacial Processes 9: 87-‐89.
6
Average October arctic sea ice coverage as observed by satellites between 1979 and 2010. Image credit: National Snow and Ice Data Center.
What normally happens in the arc7c? Albedo effects
Snow reflect solar heat, keeping the earth rela7vely cool.
As snow melts sooner with global warming, shrubs and trees invade north, crea7ng a posi7ve feedback system of more rapid warming
Barnett et al. 2005. Nature 438: 303-309.
Posi7ve feedback results from shif from reflec7ve snow, to absorp7ve shrubs and trees. Anything that decreases
albedo increases rate of warming.
Chapin et al. 2005. Science 310:657-660.
Oceans are warming Marine systems impacted as well Warmer temperatures off the coast of California have resulted in declining abundance of fish and lower productivity apart from anything else happening in the system.
The proportion of cold water species is declining, and warmer water species are increasing
Dead zones increase in size?
7
Sea-‐level is rising rapidly
-‐Sea level has recently been rising at a rate of 23 cm/century and is predicted to increase
-‐The higher rates shown are areas also subsiding. -‐The low Alaskan rate is because land is s7ll rising since last glacial epoch.
Recent data from Greenland indicates these may be underes7mates.
Sea level trends (U.S.)
Land rising faster than the ocean
Net increase in Sea Level
Sea level is rising at increased rates From 1.1-‐>3.2 mm/yr; projec7ons 4-‐17 mm/yr
Sources of sea level change
Sources of sea level rise and their contributions in mm per year for the periods 1961-2003 and 1993-2003 from the IPCC 2007 assessment. Image credit: modified from Bindoff et al., 2007 (IPCC).
NOAA 2012 Sea Level Rise Es7mates NOAA 2012 Sea Level Rise Es7mates
8
California
California Summary of model predic7ons
• Warmer temperatures mean earlier spring meltoff in the mountains
• Spring pulse of river flow shifs earlier, summer flows decline considerably
• Summer deficits of available water, reservoirs insufficient
• Terrestrial areas dry out more, increases in fire frequency, shifs in vegeta7on types
• More varia7on in weather, more violent winter storms, drier springs
• Along with sea level rise, salinity increases through estuaries
California summer temperatures
The extent of temperature rise isn’t known yet, as it depends on whether we bring emissions of greenhouse gasses down or not.
6 global climate models for each of 4 different historic and future scenarios.
The suite of models shows that northern California will increase in temperature.
The models are ambivalent about precipitation, most indicating no net change with some showing large increases or decreases. More recent models suggest less precipitation in northern California and the Sierra
Same data as previous slide shown in a different manner.
Each line represents a frequency distribution of the various models and scenarios for different years.
Net interpretation: temperature increases, precipitation doesn’t change much.
Contour diagrams of both shifts in temperature and precipitation predicted by the suite of model runs.
Next 50 yr, N. California gets warmer, same total precipitation.
Almost 100 yr from now, much warmer and precipitation may decrease.
9
Expect increased temperatures to have direct impacts on humans, as well as on natural systems.
Actual projections of changes to the Sierra Nevada Snowpack are fairly intimidating, even under a reduced emissions scenario.
Distributions of annual streamflow amounts and median-flow dates (i.e., date by which half of a year’s flow is past) in the North Fork American River, in response to 20,000 resampled climate-change realizations.
Streamflow will shift to 1) net lower annual flows, 2) earlier in the season.
Rainfall, as a fraction of total precipitation in mountains, increases through time.
Reinforces the shift of snowmelt to earlier and earlier.
Impact of shifs in snow melt and in overall snow cover
• Decreased summer flows will intensify compe7ng demands for water to meet needs of agriculture, industry and urban areas
• The health of California’s aqua7c and streamside ecosystems will be at risk
• Will shif flooding risks earlier into the winters, poten7ally coinciding with major rainfall events
• Cause major changes in what crops will be possible, and perennial crops like fruit, nuts and grapes are most vulnerable because it takes so long to replace them
Fire regimes in California
• Changes in hydrology also mean greater water stress in the summer growing seasons due to loss of water storage (earlier snowmelt, greater rainfall propor7on, higher temperatures)
• Greater water stress will decrease ecosystem produc7vity and increase fire frequencies in some vegeta7on types
10
Annual area burned is predicted to increase regardless of model parameters used.
The red line indicates a 10% increase in annual area burned. Remember this means it will take fewer years to burn what currently burns in 100 years.
Shifs in vegeta7on
Not only will changes in fire regime affect plant communities, but simple shifts in temperature will do that by itself.
Plants are limited both by absolute extremes, and also by the range of temperatures in which they can survive.
There will be major shifts in vegetation, some increasing, some declining.
-Grasslands expand into chaparral -Forests lose to shrublands -Mixed forests eliminate high elevation forests -Alpine decreases
Grasslands and Mixed Evergreen Forest are the types that increase greatly in the future .
Sea Level Rise and Levees
1100 miles of levees; a one foot rise in sea level (~30 cm) would transform the current ‘high tide peak’ from an event that occurs once every 100 years, to one that will average every 10 years
CO2
Higher Temperatures Higher Resources
Productivity (C3)
Reduced precipitation Reduced snowpack Earlier snowmelt Lower river & streamflows Higher evapotranspiration
Sea Level Rise
Salinity increases in estuaries
+ + -
-
-
Climate change and 7dal wetlands
11
Climate change and 7dal wetlands
• Uncertain about net impacts of CO2, increased temperatures, etc
• Sure about the impacts of rising sea level in rela7on to inunda7on and salinity
Subsidence & compac7on
Sea Level Rise
Rela7ve Wetland surface eleva7on
Processes contribu7ng to eleva7on decline
Sediment supply
Plant organic mamer
Rela7ve Wetland surface eleva7on
Processes contribu7ng to eleva7on increase
Potential changes in SF-Bay Delta wetlands.
Sed, SLR Sed, SLR
Sed, SLR Sed, SLR
Stralberg et al. 2011 PLoS One
Potential changes in SF-Bay Delta wetlands.
Schile et al. in press PLoS One
SLR Sed
SLR Sed
Schile et al. in press PLoS One
12
San Francisco Bay Area with a 1 m rise in sea level
Salinity (ppt)
0 5 10 15 20 25 30 35
Current Summer
Salini7es
Projected Summer
Salini7es in 2060
Figure from Noah Knowles
Projected Salinity Changes Cri7cal
Alternate scenarios of climate change
What can change these predicted scenarios? Deflected Gulf Stream?
• If Gulf Stream is deflected south, then we will cool the north temperate zone, at least temporarily.
• New data that the Gulf Steam is slowing down
The North Atlantic heat conveyor. Most warm waters in the upper ocean circulate clockwise in a giant horizontal swirl in the subtropics, but some flow farther north and cross the Greenland –Scotland Ridge (GSR). This branch warms the northern North Atlantic and Europe, and keeps most of the Nordic Seas free of ice. Here the water sinks (indicated by the star) and flows back southwards at depth, mostly down the western edge of the Atlantic basin. According to recent data, the northern branch is weakening and the latter strengthening. Bryden et al. 2005 Nature
438, 655–657
weakening
strengthening
13
Summary-‐1
• CO2 and other greenhouse gasses are being added to the atmosphere at increasing rates
• Industry, cars, etc are definitely large sources of CO2, but also land-‐use changes increasing decomposi7on
• Climate models incorpora7ng more greenhouse gasses such as CO2 indicate global warming, especially in the higher la7tudes (more as warmer winters than super-‐hot summers)
Summary-‐2
• Climate models also indicate great fluctua7ons (storm events, droughts to floods, more hurricanes, etc)
• California? Loss of snowcover, earlier water flow – more flooding in spring, drier summers, spread of salt marshes at the expense of brackish and freshwater systems or their loss, increased fire frequency, shifs in vegeta7on dominance
• Trend to warmer climates may be offset by a loss of the northern branch of the Gulf Stream, poten7ally bringing back a “limle ice age”; or increases in volcanic erup7ons might aid as well.
Most of these predictions are based on climate models. What is the confidence scientists have in these models and their predictions?
This chart shows the range for different issues.
Confidence in these Predic7ons? Final Comments
Summary? • None possible • Go into the world with your eyes opened • Enjoy climate change and the great storms we will have from now on-‐ you’ll be able to amaze your friends by predic7ng how vegeta7on around you will change
• Stun your family by charng about vasicentric tracheids or mumering “con7ngent mass-‐effects metacommunity” at the holiday dinner table
14
Final on Saturday
• Saturday, 21 December – 10:45-1:15
– 4 questions selected from a larger number
– Bring a bluebook (greenbook)