ranga myneni
TRANSCRIPT
The Greening Earth
Prof. Ranga B. Myneni
Department of Earth & Environment Boston University
USA
[email protected] http://cliveg.bu.edu/
Probing Vegetation Conference From Past to Future
July 4-‐5, 2013 Antwerp, Belgium
1/12
2/12
“La Belle Saison” René Magritte
What Happens When Radiation from the Sun Strikes a Green Leaf?
3/12
Monitoring Vegetation From Space
Image Credit: Satellite Imaging Corp.
Pigments in green leaves (notably chlorophyll) absorb strongly at red and blue wavelengths (approximately less than 0.7 microns). Lack of such absorption at near-‐infrared wavelengths results in strong scatter from leaves (approximately greater than 0.8 to 1.2 microns). The “greenness” of the ground is simply the difference between these two measurable quantities (appropriately normalized). NDVI = (NIR-‐RED) / (NIR+RED) NDVI = Normalized Difference Vegetation Index
4/12
Average Greenness Of Our Planet
“Wooded Landscape” Sir Anthony Van Dyck
How Did The Greenness of Our Planet Change?
• Satellite Vegetation Greenness Data (AVHRR) • July 1982 to December 2012 (30+ years) • 8x8 kilometer pixels • 2 Views a month
5/12
The Greening Earth
Annual Gross Productivity = Growing Season Total Vegetation Greenness Statistically signihicant (p<0.1) based on Vogelsang’s t-‐PS_T test
6/12
By How Much did the Earth Green over the Past 30 years?
• 31% of the global vegetated area greened • This greening translates to a 14% increase in gross productivity • The greening is seen in all vegetation types
7/12
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“L’Eveil de la Foret” Paul Delvaux
Why did Our Planet Green?
8/12
• 42% can be attributed to relaxation of climatic constrains to plant growth
• 57% to “other” anthropogenic factors • 1% unknown
Why did Our Planet Green?
9/12
Is this a Good or Bad Development?
Ice core record from Vostok, Antarctica: Antarctic temperature and CO2 levels Credit: Siegenthalter et al. (2005)
Credit: CLS/Cnes/Legos
Global Mean Sea Level Rise
Credit: NASA GISS
10/12
“Winterlandschap met Schaatsers en een Vogelval” Pieter Bruegel de Oude
Elfstedentocht? We Can Forget it!
11/12
The Arctic could be ice-‐free in about 30-‐50 years!
“Peasants Merry-‐Making” David Teniers de Jonge
What Can We Do? • Monitor Changes: Cost-‐effectively and accurately with Satellite Sensors • Action: Inform the Public & Policy Makers • Hope: We can be as happy as these David Teniers II’s “Peasants”
12/12