A New Look at Anthropogenic Atmospheric Carbon Dioxide David - PowerPoint PPT Presentation

A New Look at Anthropogenic Atmospheric Carbon Dioxide David Hofmann and Pieter Tans NOAA Earth System Research Laboratory Global Monitoring Annual Conference Boulder, Colorado May 14-15, 2008

Atmospheric CO 2 Atmospheric CO Growth Rates Have Been Increasing Growth Rates Have Been Increasing 400 Mauna Loa Observatory 375 Parts per Million ppm 350 per year 2 325 1.5 1 300 1950 1960 1970 1980 1990 2000 2010

Surge in carbon levels raises fears of runaway warming •David Adam Environment correspondent •The Guardian, •Friday January 19 2007 •Article history About this article Close This article appeared in the Guardian on Friday January 19 2007 on p1 of the Top stories section. It was last updated at 15:45 on September 07 2007. Mist and pollution over London. Photograph: Matthew Fearn/PA Carbon dioxide is accumulating in the atmosphere much faster than scientists expected, raising fears that humankind may have less time to tackle climate change than previously thought. From 1970 to 2000 the concentration rose by about 1.5ppm each year…. the carbon dioxide level has risen by an average 2.2ppm each year since 2001. Experts are puzzled because the spike, which follows decades of more modest annual rises, does not appear to match the pattern of steady increases in human emissions….

Processing the Mauna Loa and Global CO 2 Records: • Remove the seasonal variation (technique for filtering data to remove the seasonal variation first described by Thoning et al., J. Geophys. Res. 94 , 8549-8565, 1989). • Remove the pre-industrial component. Reduce the CO 2 concentration to that which is changing, the anthropogenic component.

Antarctic Ice Cores – Preindustrial Carbon Dioxide 295 290 Carbon Dioxide (ppm) 285 280 AVERAGE = 280 ± 2 ppm 275 270 1000 1200 1400 1600 1800 Ice Core Data: Siegenthaler, U., E. Monnin, K. Kawamura, R. Spahni, J. Schwander, B. Stauffer, T.F. Stocker, J.-M. Barnola and H. Fischer. 2005. Supporting evidence from the EPICA Dronning Maud Land ice core for atmospheric CO2 changes during the past millennium. Tellus 57B , 51-57(7).

The Mauna Loa and Global Deseasonalized The Mauna Loa and Global Deseasonalized Record Record 110 Anthropogenic Carbon Dioxide (ppm) 90 Global 70 1.43 ppm/yr Mauna Loa 50 30 1950 1960 1970 1980 1990 2000 2010

Semi-logarithmic Presentation of the Data (exponential functions are straight lines) 2.75 100 Carbon Dioxide Growth Rate (ppm/yr) Anthropogenic Carbon Dioxide (ppm) 2 Global Mauna Loa τ d = 31 yr 50 C = 280 + 34.5[exp ( l n2(YR-1958)/31)] ppm 1 dC/dt = 0.86[exp ( l n2(YR-1958)/31)] ppm/yr 0.75 30 1950 1960 1970 1980 1990 2000 2010 dC/dt ~ C ~ e t/ τ

Extrapolating Back in Time 100 Anthropogenic Carbon Dioxide (ppm) Mauna Antarctic Loa Ice Cores 10 1 0.1 1800 1850 1900 1950 2000 Ice Core Data: Siegenthaler, U., E. Monnin, K. Kawamura, R. Spahni, J. Schwander, B. Stauffer, T.F. Stocker, J.-M. Barnola and H. Fischer. 2005. Supporting evidence from the EPICA Dronning Maud Land ice core for atmospheric CO2 changes during the past millennium. Tellus 57B , 51-57(7).

While the linear CO 2 While the linear CO growth rate has growth rate has increased from increased from ~0.5 to ~2 ppm/yr, the ex ~0.5 to ~2 ppm/yr, the exponential growth ponential growth rate has rate has remained ~ constant at about 2.3 %/yr remained ~ constant at about 2.3 %/yr 10 Linear Exponential 5 Growth Rate - (ppm per year) (% per year) 1 0.5 0.1 1950 1960 1970 1980 1990 2000 2010

Using the residuals (data – function) for analysis 100 Anthropogenic Carbon Dioxide (ppm) 90 80 70 60 34.5exp[0.693(T-1958)/31] 50 40 30 5 Residual (%) 0 Agung Pinatubo -5 1950 1960 1970 1980 1990 2000 2010 The two largest negative excursions of the residuals followed major volcanic eruptions. There were no significant changes following major ENSOs (e.g.,1982-83 and 1997-98), although the 1982 ENSO may have offset an effect from the 1982 El Chichón eruption.

For the past 14 Years, the residual has been ~ ± 1 % 110 Anthropogenic Carbon Dioxide (ppm) 100 90 34.5exp[0.693(T-1958)/31] 80 70 5 Residual (%) Annual Average Residual 0 -5 1994 1996 1998 2000 2002 2004 2006 2008 2010 The annual average residual may be a useful index for detecting a deviation away from exponential growth in the future 11

WHY EXPONENTIAL? Anthropogenic C0 2 (ppm) 100 Global Mauna Loa One would expect atmospheric carbon 50 30 dioxide to follow fossil fuel emissions closely, however, this does not seem to GDP 24 be the case. The slowdown in 30 emissions following the 1973 “oil crisis” Fossil Fuel Emissions (billion tonnes CO 2 per year) was not reflected in the CO 2 record, nor GDP (trillion US dollars), Population (billions) was the reduced emission rate after 1980 ( τ d increased from 16 to 45 years). All Fossil Fuels Exponential increases are normal 10 Coal Consumption outcomes when the increase in a quantity depends on how much of the quantity exists: dC/dt ~ C. 36 5 Some that affect carbon dioxide are the Population world population and domestic production. They affect atmospheric 3 CO 2 through both sources and sinks and have similar growth rates. 1950 1960 1970 1980 1990 2000 2010 Uptake by Oceans and Terretrial Biosphere Sources: United Nations: unstats.un.org Energy Information Admin: eia.doe.gov/iea/carbon.html Carbon Dioxide Information Analysis Center: cdiac.ornl.gov Hofmann et al. (2006)

Time to 450 ppm and 2 x CO 2 for Business as Usual 400 Parts per Million (logarithmic scale) 560 ppm (2 x CO 2 ) - 2050 450 ppm - 2028 100 30 1950 1975 2000 2025 2050

SUMMARY � The deseasonalized anthropogenic component of atmospheric carbon dioxide has increased exponentially even before atmospheric measurements began. This explains why the linear growth rates have been increasing with time. � The reduction in fossil fuel emissions following the “oil crisis” of 1973 did not appreciably affect the exponential growth in the CO 2 level at Mauna Loa, nor has the recent upturn in coal consumption, a lesson for the future. Volcanic eruptions, on the other hand, seem to cause a near instantaneous response, reducing the growth rate. � The exponential behavior of CO 2 is expected considering that both Global Domestic Product and population are increasing exponentially with similar rates of growth. For these components, the exponential relation, dC/dt ~ C, is clearly expected (people and wealth beget more people and wealth). It is likely that exponential growth in CO 2 will continue until the close tie to GDP and population is broken through alternate energy sources, CO 2 sequestration and regulation.

Acknowledgements: Thanks to the ESRL/GMD Carbon Cycle Greenhouse Gases group, in particular Ken Masarie and Kirk Thoning for data analysis.