Global impacts of the 1980s regime shift

Despite evidence from a number of Earth systems that abrupt temporal changes known as regime shifts are important, their nature, scale and mechanisms remain poorly documented and understood. Applying principal component analysis, change-point analysis and a sequential t-test analysis of regime shifts to 72 time series, we confirm that the 1980s regime shift represented a major change in the Earth's biophysical systems from the upper atmosphere to the depths of the ocean and from the Arctic to the Antarctic, and occurred at slightly different times around the world. Using historical climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and statistical modelling of historical temperatures, we then demonstrate that this event was triggered by rapid global warming from anthropogenic plus natural forcing, the latter associated with the recovery from the El Chichón volcanic eruption. The shift in temperature that occurred at this time is hypothesized as the main forcing for a cascade of abrupt environmental changes. Within the context of the last century or more, the 1980s event was unique in terms of its global scope and scale; our observed consequences imply that if unavoidable natural events such as major volcanic eruptions interact with anthropogenic warming unforeseen multiplier effects may occur

Stochastic modeling of radiation regime in discontinuous vegetation canopies

International audienc

Investigation of a model inversion technique to estimate canopy biophysical variables from spectral and directional reflectance data

International audienc

Canopy spectral invariants, Part 2: Application to classification of forest types from hyperspectral data

Many studies have been conducted to demonstrate the ability of hyperspectral data to discriminate plant dominant species. Most of them have employed the use of empirically based techniques, which are site specific, requires some initial training based on characteristics of known leaf and/or canopy spectra and therefore may not be extendable to operational use or adapted to changing or unknown land cover. In this paper we propose a physically based approach for separation of dominant forest type using hyperspectral data. The radiative transfer theory of canopy spectral invariants underlies the approach, which facilitates parameterization of the canopy reflectance in terms of the leaf spectral scattering and two spectrally invariant and structurally varying variables—recollision and directional escape probabilities. The methodology is based on the idea of retrieving spectrally invariant parameters from hyperspectral data first, and then relating their values to structural characteristics of three-dimensional canopy structure

Comment On "drought-induced Reduction In Global Terrestrial Net Primary Production From 2000 Through 2009"

Zhao and Running (Reports, 20 August 2010, p. 940) reported a reduction in global terrestrial net primary production (NPP) from 2000 through 2009. We argue that the small trends, regional patterns, and interannual variations that they describe are artifacts of their NPP model. Satellite observations of vegetation activity show no statistically significant changes in more than 85% of the vegetated lands south of 70° N during the same 2000 to 2009 period.3336046Zhao, M.S., Running, S.W., (2010) Science, 329, p. 940Nunes, E.L., (2008), www.biosfera.dea.ufv.br/phtm/teses/pdf/DS_EdsonNunes.pdf, thesis, Federal University of Vicosa available atCosta, M.H., Nunes, E.L., Senna, M.C.A., Imbuzeiro, H.M.A., (2009) Brazilian J. Meteorol., 24, p. 179Turner, D.P., (2006) Remote Sens. Environ., 102, p. 282Vieira, S., (2004) Oecologia, 140, p. 468Aragão, L.E.O.C., (2009) Biogeosciences Discuss., 6, p. 2441Zhao, M.S., Heinsch, F.A., Nemani, R.R., Running, S.W., (2005) Remote Sens. Environ., 95, p. 164Samanta, A., (2010) Geophys. Res. Lett., 37, pp. L05401Phillips, O.L., (2009) Science, 323, p. 1344Llovel, W., Becker, M., Cazenave, A., Cretaux, J.F., Ramillien, G., (2010) C. R. Geosci., 342, p. 179Myneni, R.B., Hall, F.G., Sellers, P.J., Marshak, A.L., (1995) IEEE Trans. Geosci. Rem. Sens., 33, p. 481Tucker, C.J., Fung, I.Y., Keeling, C.D., Gammon, R.H., (1986) Nature, 319, p. 195Myneni, R.B., Keeling, C.D., Tucker, C.J., Asrar, G., Nemani, R.R., (1997) Nature, 386, p. 698Nemani, R.R., (2003) Science, 300, p. 1560Ciais, P., (2005) Nature, 437, p. 52