Environmental Issues CHAPTER 21
Axial Tilt
-22.1-24.5 degrees... 23.4 degrees tilt right now -cycle of 41,000 years
Central Case: Shift in start of fire season globally
-A forest fire in May 2007 claimed 75,000 acres of boreal forest near Ham Lake in the North Woods of Minnesota -Size was not surprising but timing was -For scientists who have been studying forests for decades, it was just one more sign that the climate is changing
Earth's climate system
-About 30% of incoming radiation is immediately reflected back to space -Atmosphere, clouds, land, ice, and water absorb remaining 70% of incoming radiation -Some is reradiated to space, some stays trapped in atmosphere
Current climate change has both human and natural causes
-Anthropogenic: caused or related to human action -Computer models take factors known to have affected past climates to see what might be responsible for recent warming
Orbital Eccentricity
-Earth's current orbit is round -warmer when most elliptical -Cycle of 100,000 years
North American Deep Water (NADW)
-Europe much warmer than would be without movement of this heat -Agriculture enhanced, cost of heat production reduced
Core Message of Chapter 21
-Evidence for climate change is overwhelming; human activity is primarily responsible -Climate change is impacting species, ecosystems, and human health and well-being with more change expected -Scientific investigations have provided valuable information about the past -Also offer clues about what to expect and how to deal with changes to come
Climate change has consequences - health impacts
-Expansion of tropical diseases to now temperate areas -Heat waves and heat stress can cause death (even drownings) -Increase in rates of respiratory ailments, disease and sanitation problems, hunger-related issues due to failing crops in drought stricken areas -Adaptation: health programs to protect from infections, provide ways to cool and clean air for most vulnerable, get food to those in need
Warmer oceans absorb less CO2
-Gases less soluble in warmer water -Further accelerates warming
Melting snow and ice
-Glacier mass decreased -Worldwide, nearly all mountaintop glaciers disappearing -As ice melts, darker, less-reflective surfaces are exposed and absorb more sunlight, causing more melting -Glacier National Park (MT): 150 glaciers when park created in 1910 -2010: 37 remain, only 25 "active" (>25 acres) -All glaciers expected to be gone by 2020-2030
Sulfate-rich volcanic eruptions can be cool
-Haze reduces sunlight reaching and heating Earth's surface -1991 Mt. Pinatubo eruption dropped mean global temp by .9 degrees F for 1 year
Ice and snow cap of Mount Kilimanjaro disappearing
-Ice on cap in 2007 was 85% smaller than cap in 1912 -Shrank 1%/yr from 1912-1963, 2.5%/yr from 1989-2007 -Decreased albedo accelerates melt -Increased temperatures and decreased snowfall
Intergovernmental Panel on Climate Change (IPCC)
-International panel of scientists and government officials established by U.N. in 1988 -Most thoroughly reviewed and widely accepted synthesis of scientific information on climate change -Has issued a number of reports on climate change every few years
Other melting Snow and Ice problems
-Land-based annual snowpack and glacial melt in mountains of world supply water for billions of people -Greenland ice sheet also rapidly melting -In Antarctica, ice shelves the size of Rhode Island have recently cleaved off and disintegrated -Glacial times are cyclical, but perhaps fewer than 1 million people on planet last time so few glaciers (7,400 times more people now) -Russia, U.S., Canada, Norway, and Denmark claiming regions of the Arctic as ice sheet melts (Access to underwater petroleum and mineral reserves)
Potential solutions for Mitigation
-More efficiency at plants -Less coal burning (like none) -Continue shift to natural gas as a transition to renewables -Nuclear Power -Renewables: hydroelectric power, geothermal energy, solar photovoltaic cells, wind -Energy conservation by consumers
Why would only a few degrees matter?
-National Oceanic and Atmospheric Administration (NOAA) data = recent global average land temperatures are almost 2 degrees F higher than the mid-20th Century average -During the last ice age (20K yrs ago), when an ice sheet extended as far south as Chicago (and central IA), average temperature was only 5.5 degrees F colder than mid-20th Century
Sulfate geoengineering for reflecting sunlight outward
-Rockets, balloons, jets inject sulfate aerosols into upper atmosphere -Multi-billions of dollars per year to deliver particles
More proxy indicators
-Scientists drill cores into sediments of ancient lake beds -Pollen grains in each layer indicate types of plants growing there at each time -Also can look at tree rings to infer rain and fire history -Accretion patterns in coral reefs reveal aspects of ocean chemistry -Woodrat middens preserve plant parts, scavenged items, and feces for centuries or millennia
Studying climate change: Direct sampling
-Scientists have recorded CO2 levels in atmosphere directly since 1958, at a station in Hawaii -Data show a steady upward climb in annual mean from 315 to 404 ppm from 1958 to 2016
Climate change has consequences - biodiversity losses
-Some species may benefit, but most will suffer due to rapid rate of change (Community decoupling) -Shifting geographic ranges: some species mobile enough to move poleward or uphill; until there's nowhere to go -Coral reefs (2nd most diverse ecosystem) -Warmer waters & acidification lead to bleaching and impaired growth -Adaptation: Wildlife and habitat management to provide migration corridors or relocation assistance; protect vulnerable habitats from further impact
Relationship between temperature and atmospheric CO2
-Two parameters closely aligned over past 400K years -Appears to be one of both cause and effect -In past, natural events triggered warming → release of more CO2→ even more warming
Climate change has consequences - crop losses
-Under scenario of slight temperature increase, crop production could be expected to increase (More CO2 and longer growing season) (But plants quickly acclimate to higher CO2 and need more water to grow well) -With higher temperature increases, crop yields will fall -More prolonged droughts, extreme floods -Shifting of agricultural belts poleward -Adaptation: Use strong erosion-control techniques and choose crops to fit the new conditions in given area
Does not explain recent century-long heating trend
-Variation in solar energy has not been great enough to change Earth's temperature -Estimated to be tiny fraction compared to human causes of atmospheric gas composition changes
Axial Precession
-Vega - leaning left -North Star - leaning right (Currently in this) -Cycle of 19,000-23,000 years
On a warming planet, we should see:
-Warmer average temperatures -higher number of extreme weather events than normal -melting sea ice -rising sea levels -precipitation change -All of these are currently being observed
Evidence of global climate change abounds
-Warmer temperatures lead to more evaporation -Can be expected to lead to weather extremes -Precipitation changes since 1951
ENSO cycles
-periodic, every 2-8 years -Globally warming air & sea temps may be increasing frequency and strength of these events
La Niña
-the opposite; cold water spreads west -Weather patterns affected in opposite way
Temperature increases: what's been observed
1. Average surface temperature rose 0.74°C in past century -1990s the warmest decade in past 1,000 years -Then came the 2000s -2011-2015 is hottest 5-yr period on record 2. 16 warmest years recorded come from last 18 years 3. 2016 on track to top list and break record
Primary causes of atmospheric increase in CO2
1. Burning of fossil fuels in homes, factories, and automobiles -Remove and combust carbon-rich fuels from the ground (lithosphere) where they have been stored for millions of years, sending CO2 into the atmosphere 2. Deforestation: Cutting down trees, removing vegetation from the land -Burning to clear land (no net change) -Decreases land's ability to suck up CO2 from atmosphere
Coastal areas will flood
1. Cities will continue to be flooded -53% of U.S. population lives in coastal areas -Already happens annually in Asia (1,000s dead per storm not uncommon) -Pakistan floods of 2010: 307,000 sq. miles under water (that's 5.5 Iowas) 2. Millions of people will be displaced from coastal areas 3. IPCC predicts mean sea level to be 18-59 cm (7-23 in) higher than today at end of 21st century
Atmospheric carbon dioxide concentrations
1. Concentration has increased 47% in the past 200 years ~275 ppm all of human history until ~1800 -Yearly average of 404 ppm in 2016, rising 2 ppm/yr -For science behind "The most important number in the world" - Bill McKibben, check out www.350.org 2.Now at its highest level in 800,000 years, and probably highest in past 20 million years
The debate that isn't actually one
1. Despite broad scientific and military leadership concern that climate change is a pressing issue, it remains mired in an outdated debate 2. Debate fanned and funded by industry-based skeptics, free-market proponents, and "think tanks" -Fear of new costly government regulations or affiliation with international bodies (like the UN) -Goal to cast doubt on scientific consensus
Climate change has consequences - fire risk
1. Fires have increased in many areas -Larger and at abnormal times -Come into contact with areas of higher population density -Nov-Dec. 2016: 19 fires across 6 SE states, burned 16,000 acres in Great Smoky Mountains 2. Projected to increase further in future 3. Adaptation: Pursue better fire-prevention (or management) techniques; improve fire response plans
Global warming potential of GHGs
1. Global warming potential: relative ability of 1 molecule of a given GHG to contribute to global warming 2. Carbon dioxide (CO2) is the primary greenhouse gas -Not most potent GHG, but extremely abundant -Emissions of GHG from human activities mostly CO2 3. GHGs vary in global warming potential; over 100 years in atmosphere: -Methane (CH4 ) traps ~25 times the heat of CO2 -Nitrous oxide (N2O) traps ~298 times the heat of CO2 -Hydrofluorocarbon-23 traps ~14,800 times the heat of CO2
Increase of other greenhouse gases PART 2
1. Halocarbon gases (which include CFCs) are powerful GHGs (14,800X stronger than CO2) -Used as refrigerants, propellants, cleaning solvents since invented in 1930s -Fluorine with bromine or chlorine has effects on ozone layer, too -Effects are slowing due to the Montreal Protocol of 1987, which required phase out of use of CFCs 2. Water Vapor is the most abundant greenhouse gas -Concentration depends on air temperature -Not changed significantly in recent centuries -Therefore, not viewed as major driver of industrial-age climate change
Extreme weather events increasing
1. Intensity of storms may be increasing with increased energy in atmosphere -762 U.S. tornadoes in April 2013 was 367% above monthly average 2. Higher sea surface temperature leads to more big storms -Frequency of Atlantic hurricanes doubled over last century 3.More snow in winter with a warmer atmosphere
Ocean circulation PART 2
1. Interrupting thermohaline circulation could trigger rapid climate change 2. If Greenland's ice melts, freshwater runoff would dilute surface waters, make them less dense, and slow or stop NADW -Data suggest circulation already is slowing
Increases of other greenhouse gases PART 1
1. Methane (25X stronger than CO2) -Up 151% since 1750 -From fossil fuels, organic decay in landfills, cattle, rice crops 2. Nitrous oxide (298X stronger than CO2 ) -Up 18% since 1750 -From feedlots, chemical plants, auto emissions, agricultural practices For both of these GHGs, highest concentrations in 800,000 or more years
Rising Sea Levels
1. Sea levels have risen 10-20 cm over last century 2. Rate of increase accelerated since 1993 3.Land-based glaciers and ice sheets melting -Increased flow into the oceans 4.Oceans warming -Warming water expands in volume
Precipitation patterns already changing
1. Some regions receiving more precipitation than usual, and others receiving less -Iowa wetter than average past 15-20 years 2. Droughts have become more frequent and severe -Harms agriculture, promotes soil erosion, reduces drinking water supplies, encourages forest fires, increases conflict between regions and users 3. Heavy rains have contributed to flooding -Killing people, destroying homes, and inflicting billions of dollars in damage 4.Greater variability in frequency and intensity of storms
Sulfate - Some Small Problems
1. Sulfates subject to gravity 2. Long-term program: stop and you have rapid heat up 3. Sulfates can degrade upper-atmosphere ozone layer 4. Clumping of sulfate particles would warm atmosphere 5. Alters regional sunlight and rainfall patterns -Rapid cooling means less water vapor, less precipitation, more droughts, agricultural collapse in some areas
Three objects influence Earth's climate more than all others combined
1. Sun - Provides most of Earth's energy 2. Atmosphere - Absorbs energy from the sun and reflects some back into space 3. Oceans - Store and transport heat and moisture
Ways to reduce transportation emissions
1. Technology: hybrids, electric, CNG, biodiesel, hydrogen 2. Reduced automobile usage -2008 was first year ever a decline in miles driven in U.S. 3. Biking or walking to work or run errands (health benefits, but requires infrastructure changes) 4. Using public transportation -If Americans used public transport at same rate as in Europe (10% of daily travel), U.S. would no longer need to import Saudi Arabian oil
Mitigation options - transportation emissions PART 1
1. Transportation is 2nd largest source of GHGs -1/3 of average U.S. city devoted to cars (Roads, parking lots, garages, gas stations, etc.) 2. Average U.S. family makes 10 car trips/day 3. $200 million per day on road construction and repairs 4. 2009 stimulus funds fixed roads and bridges, no public transit 5. Pres. Elect Trump's infrastructure plan: $1T over 10 yrs
Ocean circulation PART 1
1. ocean water exchanges tremendous amounts of heat with the atmosphere 2. Dense cold water sinks at poles and moves toward equator 3. Water column heated at equator and pushed/pulled to poles -Moves energy from place to place -Without it, poles would be even colder, and equatorial areas even warmer
Adaptation & Climate Change
Accept climate change is happening and pursue strategies to minimize its impacts on life -Use technology and engineering, adjusting farming to cope with droughts, etc. -Sometimes criticized as sidestepping
Aerosols and climate
Aerosols (microscopic particles and droplets) in the atmosphere can warm the climate (soot), but most aerosols can lead to atmospheric cooling -Sulfate aerosols produced by fossil fuel combustion may slow global warming in short term -Does it balance effect of CO2 produced by combustion? -Sulfate aerosols create acid rain
El Niño
Air pressure increases in W Pacific and decreases in E Pacific, weakening equatorial winds -Water flows eastward, suppressing upwellings, shuts down delivery of nutrients to aquatic life -Coastal industries devastated; regional & global weather changed
Mitigation & Climate Change
Alleviate problem, or pursue actions that reduce greenhouse gas emissions to lessen severity of future climate change -Hard to do: ↑ renewable energy, ↑ efficiency, ↓ carbon footprint of industrial agriculture, ↓deforestation
GHGs
Atmospheric gases that absorb infrared radiation are called greenhouse gases -Water Vapor, CO2, CH4, CFCs and HFCs, N2O, O3 -CO2: 64% -Methane (CH4): 17% -CFCs & HCFCs: 13% -N2O: 6%
GHGs affects
By absorbing and re-emitting radiation, they warm Earth's atmosphere and surface, like a greenhouse... Called greenhouse effect -A natural phenomenon, some necessary -Part of atmosphere for billions of years
Global Climate Change
Changes in Earth's climate -Broader scope than simply global warming (an increase in Earth's average surface temperature) -Temperature, precipitation, and variation in timing and intensity of events (storms, droughts) -No single weather event can be attributed to climate change, but rapid shift in temp. ranges indicate change
Future effect of water vapor in a warming climate?
Could cause positive feedback and speed up global warming -Temperature increase: more vapor transferred air, amplifying the greenhouse effect Could cause negative feedback and slow global warming -More vapor could lead to more clouds, reflecting more incoming solar radiation back into space
Mitigation options - electricity generation and usage
Electricity generation is the biggest source of greenhouse gas emissions in the U.S.
10 Indicators of a Warming World
GOING DOWN -Sea Ice -Glaciers and Ice Sheets -Snow Cover GOING UP -Water Vapor -Temperature Over Oceans -Sea Surface Temperature -Ocean Heat Content -Sea Level -Air Temperature Near Surface (Troposphere) -Temperature Over Land
Studying climate change: Indirect sampling
How do we know about what climate was like in the past, before we were here? -Proxy Indicators
Proxy Indicators
Indirect lines of evidence that substitute for direct measurements -Ice caps, ice sheets, and glaciers accumulated over thousands or millions of years -Scientists drill cores, analyze gas bubbles in each layer to see what the atmosphere was like -Atmospheric composition, greenhouse gas concentration, temperature trends, snowfall, solar activity, and frequency of fires -Comparing values for indirect indicators with direct sampling values for same time lets us see what the world must have been like before -Assuming laws of nature operate same as before
What to do about climate change?
Mitigation and Adaptation; both probably necessary
Mitigation options - transportation emissions PART 2
Number of cars ever growing -In U.S. equal numbers of cars and people Cars use energy very inefficiently -Only ~14% of fuel energy used to move car forward -Remainder lost to heat, friction, idling, accessories
Ocean absorption
Ocean holds 50 times more carbon than atmosphere and absorbs it from atmosphere -Carbon absorption by the oceans has slowed global warming but is not preventing it -Adding CO2 faster than water or life can absorb it -Reaching CO2 saturation levels -CO2 load making oceans more acidic
Climate change has consequences - coastal erosion and flooding
Property losses projected to increase -Rising sea levels -More frequent, intense rainfall events Adaptation -Relocation of some coastal communities may be necessary -Construct protective barriers and restore wetlands in coastal areas to protect inland areas
Climate change has consequences - drought
Proportion of land area in severe drought already increasing -High evaporative loss and changes in precipitation patterns Adaptations -Fund and build structures to capture and conserve water -Practice pollution prevention to increase and protect water supplies -Use sustainable farming techniques for that location
Milankovitch Cycles - what are they?
Recurring patterns in tilt and orbit -Alter way solar radiation is distributed over Earth's surface -By modifying patterns of atmospheric heating, cycles can trigger long-term climate variation such as periodic glaciation
Climate change is like, a thing
Scientific evidence that climate has changed since industrialization now overwhelming and indisputable
Solar output
Sun varies in radiation it emits -At each peak of 11-year sunspot cycle, sun emits flares strong enough to disrupt satellite communications -Extra radiation can increase radioactive forcing
Other ways to reduce emissions
Use advances in agriculture, forestry, and waste management -Use sustainable land management -Grow renewable biofuels -Reforestation, sustainable forestry, forest preservation -Recovering methane from landfills, wastewater treatment -Recycling, composting, and reduction or reuse of materials
Regional and global climate
Varies over time naturally -But rate of recent rapid warming of planet and change in atmospheric composition has never been this high -Scientific consensus that human activities have changed the composition of our atmosphere
Temperature change not evenly distributed
Weather patterns of Ellesmere Island in Arctic -Spring and summer temperatures 20−29 degrees F higher than in previous years -Difference equivalent to locations 1,000-1,400 miles farther south
Climate and climate change
Weather: conditions at localized sites over hours or days -Temperature, humidity, wind, precipitation, etc. Climate: larger region's long-term pattern of atmospheric conditions, typically little variation year-to-year
Rising atmospheric concentrations of CO2
Why the within-year variation in CO2 levels at this location? -Depends on seasons, plants only produce a lot of CO2 spring through late summer
Climate change
alteration in the long-term patterns and statistical averages of meteorological events
Intergovernmental Panel on Climate Change (IPCC)
an international group of scientists that evaluates scientific studies related to climate change to thoroughly and objectively assess the data
Radiative forcer
anything that alters the balance of incoming solar radiation relative to the amount of heat that escapes out of space
Anthropogenic
caused by or related to human action
Positive feedback loop
changes caused by an initial event that then accentuate that original event (a warming event gets even warmer)
Negative feedback loop
changes caused by an initial event that trigger events that then reverse the response (warming leads to events that eventually result in cooling)
Adaptation
efforts intended to help deal with a problem that exists, such as climate change
Mitigation
efforts intended to minimize the extent or impact of a problem such as climate change
Climate
long-term patterns or trends of meteorological conditions
Greenhouse gases
molecules in the atmosphere that absorb heat and reradiate it back to Earth
Milankovitch cycles
predictable variations in Earth's position in space relative to the Sun that affect climate
Albedo
the ability of a surface to reflect away solar radiation
Weather
the meteorological conditions in a given place on a given day
Global Warming
the observed and ongoing rise in the Earth's average temperature that is contributing to climate change
Greenhouse effect
the warming of the planet that results when heat is trapped by Earth's atmosphere
