Ref: D. Fahey, adapted from IPCC 4th Assessment, Summary for Policymakers, Feb. 2, 2007

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WHAT ARE THE MAJOR HUMAN & NATURAL ACTIVITIES FORCING CLIMATE CHANGE IN THE INDUSTRIAL ERA (1750-2005)?

1.6 W m-2 x 5.1 x 1014 m2 = 8.16 x 1014 W = 816 TW (about 52 times current global energy consumption)!

RON PRINN, MIT-FEN LUNCHEON TALK, 10/14/08

Global Cycles of Greenhouse Gases are studied using Measurements & Global Circulation models28-level 1.8ox1.8o Model for

Atmospheric Transport & Chemistry (MATCH) uses NCEP meteorology

AGAGE measures 45 gases 20-36 times per day at globally distributed

stations dating back to 1978

How well do we understand Greenhouse

Gas (GHG) Cycles?

AGAGE NETWORK STATIONS

Hateruma (Japan)Mt. Cimone (Italy)

Jungfraujoch (Switzerland) Ny-Alesund (Norway)

AGAGE INSTRUMENTATION1. Medusa GC-MS

2. GC-Multi-detector3. Calibration

MONTREAL PROTOCOL GASES & THEIR REPLACEMENTS

Radiative Forcing from Carbon Dioxide and other Greenhouse gases

N2OCFCs

others

TRENDS IN METHANE: WHY DO THEY VARY INTERANNUALLY AND WHY HAVE THEY

DECELERATED IN RECENT YEARS?

QUASI-STEADY STATE: Emissions(CH4) ~ k[OH].Content(CH4) ?Ref: IPCC 4th Assessment, Summary for Policymakers, Feb. 2, 2007

AGAGENOAA

• High-Frequency (13: AGAGE, NOAA, etc.) and Flask (41 comprehensive & 32 more intermittent: NOAA, CSIRO, etc.) monthly mean observations between 1996-2001

• Interannually varying transport (NOAA/NCEP) used in 3D MATCH model (T62, 1.8o x1.8o, 28 levels, 1000-2.9mb) to create the CH4 response of each site to monthly pulses from individual regional processes (sensitivity H(t) matrix)

• Kalman Filter used to solve for: (a) 7 Seasonally-varying processes as monthly varying fluxes (b) 2 Pseudo-steady processes as constant fluxes using annually repeating time/space varying MATCH model OH tuned to AGAGE CH3CCl3 observations

METHANE INVERSE STUDIES USING 3D MATCH MODEL (Chen & Prinn, 2005, 2006)

El Nino winds

La Nina winds

AGAGE observations versus MATCH model at Samoa

MIRROR PLOT

MATCH Simulates Effects of ENSO Transport on CH4

Ref: Chen & Prinn, J.G.R., 2005

SUMMARY: AVERAGE SEASONAL CYCLES (SELECTED AND ALL DATA SETS)

CAPTURES EXPECTED SEASONAL CYCLES (RICE PEAKS EARLIER)

ReferenceHigh Freq.AllBest

Ref: Chen & Prinn, J.G.R., 2006

Summary: Interannual variability (Monthly Anomalies) 32-33 Tg yr-1 Total Emission increase in 1998 with8-17 Tg yr-1 due to Rice regions Northern/Tropical Wetland and Rice Region Emissions dominate the total variability

Fluxes in Tg yr-1 Northern Wetlands

Tropical Wetlands

Inversion 5-10 8.3-9.9Bottom-up* 12 13

BUT Boreal Fires in Siberia may have also contributed to our deducedstrong Northern wetlands increase

*wetland model driven by 1998 record temperature and large precipitation anomalies (Dlugokencky et al. (2001))

1998 wetland Flux Anomalies

Summary: 5-year averages

_ (literature)

(1) ENERGY RELATED EMISSIONS SMALLER (RUSSIAN GAS LEAKS?)

COMPARED TO PREVIOUS ESTIMATES:

(2) RICE RELATED EMISSIONS LARGER (PROXIMAL WETLANDS OR TROPICAL ECOSYSTEMS?)

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METHANE IS RISING

AGAIN, BUT WHY?

(TRENDS AT AGAGE & CSIRO STATIONS)(Rigby et al, 2008)

RESULTS FOR

EMISSION ANOMALIES

FROM INVERSIONS

(Rigby et al, 2008)

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The hydroxyl free radical (OH) is the major oxidizing chemical in the global atmosphere

It annually removes about 3.7 billion metric tons of trace gases (CO, CH4, higher hydrocarbons, hydro-halocarbons, NOx, SOx, etc.) from the atmosphere..Are the levels of this dominant cleansing chemical changing? A decrease is dangerous!With a lifetime of only about 1 second it is possible to measure locally, but not possible to measure directly at regional to global scales.Use AGAGE measurements of the industrial chemical CH3CCl3, whose major sink is OH, to indirectly estimate large scale OH variations.

Ref: Update of Prinn, Huang et al, G.R.L., 2005

The inferred OH minima generally coincide with strong El Nino’s and/or massive global wildfires (updated from Prinn, Huang, et al, G.R.L.,2005). The 2006-2007 drop is therefore unexpected.

Global weighted average OH inferred from AGAGE CH3CCl3

12.335(U) / 12.835(G)Experimental Atmospheric Chemistry (Fall

2008)Logistics:

Lectures: Tuesdays (usually), 12:30-2:30pm, Room 54-1510Lab Periods: Thursdays (usually), 12:30-2:30pm, Room 54-1811

4 Field Trips: Sun: 9/7, Fri: 10/10, Sat: 11/1, Sat: 11/15Attendance at lectures, labs and especially field trips is mandatory.

Instructors:Ronald G. Prinn, 54-1312, rprinn@mit.edu

Laura Meredith, 54-1320, predawn@mit.eduKat Potter, 54-1414, kep@mit.edu

Grading: 10% - Participation

20% - Topic 1 - CO2 & Climate20% - Topic 2 - CFCs & Ozone Layer

20% - Topic 3 - Air Pollution & Health30% - Topic 4 - Tropospheric Photochemistry - [20% - Lab Report, 10% - Presentation]

Each student will focus on a chosen aspect of tropospheric photochemistry for their topic 4 lab report and presentation.

A list of possible subjects will be provided mid-semester and student selections are due on Nov. 17th.

Credit: 2-2-8 Undergraduate or Graduate Credits

Stellar website: http://stellar.mit.edu/S/course/12/fa08/12.335/

Ref: D. Fahey, adapted from IPCC 4th Assessment, Summary for Policymakers, Feb. 2, 2007

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