Attribution of Extreme Weather & Natural Gas, Fracking and - - PowerPoint PPT Presentation
Attribution of Extreme Weather & Natural Gas, Fracking and Methane Leaks Steve Pacala Princeton University February 2016 Attribution of Extreme Weather Humans are moved to action by personal, immediate and tangible threats. We seem to
Humans are moved to action by personal, immediate and tangible
Climate change is seen as remote, impersonal and intangible. What does 2 degrees of global warming mean to me? This appears to be changing because of surprisingly rapid changes in extreme weather. You may have heard that it is impossible to attribute any one extreme weather event to climate change. This is no longer true.
Attribution of heat waves (the greatest killer), extreme precipitation (the greatest damager of property), drought (including the Californian drought) and some aspects of hurricanes (a portion of the coastal flooding) is already a fixture in the mainstream, peer reviewed scientific literature. Real-time attribution within the news cycle is just around the corner. This may be climate’s smoking and cancer moment.
Moscow or 2003 European events.
Africa.
independent studies)
IPCC AR5 It is virtually certain that internal variability alone cannot account for the observed global warming since 1951. It is virtually certain that human influence has warmed the global climate system.
IPCC AR5 Global Mean Temperature Model-Data Comparison With and Without Anthropogenic Forcing
Return time in the 1990’s for an extreme with a 20-year return time in the 1960’s 1960’s coldest nighttime low in 20-years
38 years in the 1990’s Coldest daytime high 1960’s hottest nighttime low in 20-years
years in the 1990’s Hottest daytime high Model- estimates of changes due solely to anthropogenic GHG’s and aerosols.
Severity
Frequency
80 90 100 110 120 130 140 150 200 400 600 800 1000
Severity
Return Time = 1/ Frequency
Severity Frequency
80 90 100 110 120 130 140 100 200 300 400 500 600 700 800 900 1000
Return Time Severity Without anthropogenic forcing RN
= 1/950.
With anthropogenic forcing RA,N
= 1/380
IPCC AR5 (2013) IPCC Special Report on Extremes (2012)
special reports on the previous year’s extreme events.
2012 2013 2014
BACKGROUND: Natural gas is used primarily for electricity production and heating and could be used as a dominant transport fuel. Gas, coal, nuclear and hydro are our only significant sources of base-load
solar are limited by our inability to store energy at grid scales. EVIRONMENTAL BENEFIT: For the same useful energy gas has half the CO2 emissions of coal and three quarters that of oil. ENVIRONMENTAL COSTS: 1. Natural gas leaks could eliminate its greenhouse advantage because methane (CH4), the primary component of gas, is 120 more potent as a greenhouse agent than
adoption of renewables.
Dispute about methane leaks:
6%), making gas worse than coal.
regulation is required. A consortium including the Environmental Defense Fund, 10 big gas producers, and many academics measured the leaks from the US infrastructure.
0.2 0.4 0.6 0.8 1 1.2 20 40 60 80 100
Fraction of Mass Remaining Time (years)
CO2 CH4
CH4 is converted in the atmosphere to CO2 with a half life of ~12 years. CO2 has a complex residence time in the atmosphere but a large fraction remains for 100’s of years.
Radiative forcing
Time (years)
But remember that CH4 in the atmosphere creates 120 times more radiative forcing than an equal mass of CO2 : Note that the radiative forcing from a pulse of either CH4 or CO2 decreases over time, but the CH4 forcing decreases faster.
*Radiative forcing values are normalized so that a unit mass
0.1 1 10 100 50 100
CO2 CH4
20 40 60 80 100 120
20 40 60 80 100 120 10 20 30 40 50 60 70 80 90 100
Methane GWP Time Horizon (years)
There is no scientifically correct value for the time horizon!
The Global Warming Potential The commonly used measure of the climate impact of a greenhouse gas is the cumulative radiative forcing for the gas relative to that of CO2. For methane, this is the cumulative radiative forcing caused by a pulse of CH4 emission up to TH years, divided by the corresponding forcing from an equal-mass emissions of CO2.
Fugitive Emissions from production, processing and distribution, scaled to the gas used by the plant. CO2 emissions from the gas plant. Methane emissions from coal mining scaled to the coal consumed by the plant. CO2 emissions from the coal plant.
Note that this depends on TH! TWP(TH)’s can be used to compare any two technologies that emit CH4 and/or CO2.
CH4 GWP. CH4 GWP.
To compare the climate change from a gas and coal power plant, one uses a “technology warming potential” (TWP(TH)) (Alvarez et al. 2012, PNAS):
Because this is less than 1 for all TH, gas is always better than coal if EPA methane emissions estimates circa 2011 were correct. TH: CNG vs. Gasoline Car CNG vs. Heavy Diesel Truck Combined Cycle Gas
Time since the switch to gas.
Dotted line: TWP(TH) showing the effect of a single pulse of operation (i.e. a day). Dashed line: TWP (TH) for a pulse lasting the lifetime of the infrastructure (50 years for a power plant). Solid line: TWP(TH) for a permanent switch from coal to gas (i.e. the pulse persists from zero to TH).
Using an EPA estimate that 2.4% of methane is emitted during gas production, processing and distribution, and other assumptions in Alvarez et al. (2012, PNAS):
From Alvarez et al. 2012. PNAS
Note that this is 0.9% smaller than EPA estimate in Alvarez et al. (2012).
Top-down and bottom-up emissions almost never agree.
Top-down measurements:
7 separate estimates from aircraft methane measurements. 6 separate estimates from aircraft ethane measurements.
Bottom-up measurements:
1 extensive random sample 3 extensive non-random samples targeting the rare high emitters that dominate the total emission rate. The non-randomness is correctly accounted for when integrating the random and nonrandom samples.
Helicopter Infrared:
Imagery of large sample production wells, compressors and processing plants.
In the end: