Large Variations in Southern Hemisphere Biomass Burning During the Last 650 Years
Z. Wang, J. Chappellaz, K. Park, and J. E. Mak. 2010. Large Variations in Southern Hemisphere Biomass Burning During the Last 650 Years. Science Express 2 December 2010.
Full text [here]
Selected excerpts:
Abstract
We present a 650-year Antarctic ice core record of concentration and isotopic ratios (d13C and d18O) of atmospheric carbon monoxide. Concentrations decreased by ~25% (14 ppbv) from mid-1300s to the 1600s, then recovered completely by the late 1800s. d13C and d18O decreased by about 2% and 4% respectively from the mid-1300s to the 1600s, then increased by about 2.5% and 4% by the late 1800s. These observations and isotope mass balance model results imply that large variations in the degree of biomass burning in the Southern Hemisphere occurred during the last 650 years, with a decrease by about 50% in the 1600s, an increase of about 100% by the late 1800s, and another decrease by about 70% from the late 1800s to present day.
… The main sources of atmospheric CO include atmospheric oxidation of methane and non-methane hydrocarbons (NMHC), biomass burning, and fossil fuel combustion (4). These sources account for about 90% of today’s global CO budget (4). Stable isotopic ratios (d13C and d18O) in atmospheric CO help to resolve the relative contributions of these sources and thus to better estimate the global CO budget (5). To date, no isotopic ratios from CO in ice have been reported and few CO mixing ratio measurements have been reported (1, 3, 6). Using a recently developed analytical technique (7), we present measurements of CO concentration ([CO]), d13C, and d18O from a South Pole ice core… and from the D47 ice core… in Antarctica (Fig. 1). …
The contribution from fossil fuel combustion is negligible prior to the 1900s based on historic CO2 emissions from fossil fuel combustion (10). In addition, simulations from the Model for Ozone and Related chemical Tracers (MOZART-4) (see Supporting Online Material, SOM) shows the fossil fuel combustion contribution to today’s CO budget in Antarctica is only 2-3 ppbv. Thus the main sources of CO able to explain our signals are biomass burning and NMHC oxidation. …
We can use isotopic compositions to help distinguish combustion-derived CO (e.g., biomass burning) from non-combustion derived CO (e.g., hydrocarbon oxidation). C18O is a useful tracer for this because of large differences in the oxygen isotopic composition between combustion and noncombustion sources of CO (11). The d18O signature from combustion sources is significantly enriched compared to the d18O signature from hydrocarbon oxidation processes (11-12). d18O value for biomass burning derived CO is generally between 15% and 22%, depending on specific combustion conditions (12–14). …
CO from NMHC oxidation did not change significantly, whereas CO from biomass burning showed a large “saddle” trend, with maxima in both the mid-1300s and the late 1800s and a minimum in the 1600s. The observed trend in [CO], d13C and d18O was therefore mostly driven by variations in biomass burning, and compared to present day, biomass burning was almost the same in the late 1800s as that in the mid-1300s. …
Previous modeling studies suggest that preindustrial biomass burning was much lower than today, with a reduction of up to 90% (35–37). This is the common assumption in climate model simulations. However, our results show that present day CO from Southern Hemisphere biomass burning is lower than at any other time during the last 650 years. This is particularly relevant since assumptions on preindustrial [CO] are an important component for correctly estimating the radiative forcing of tropospheric ozone in preindustrial times (38). [CO] changes due to biomass burning also suggest that there were decadal and centennial scale variations in average concentrations of black carbon, another major atmospheric constituent produced with burning, leading to the unanswered question of its potential role in long term climate variability.
Changes in Snowfall in the Southern Sierra Nevada of California Since 1916
John R. Christy and Justin J. Hnilo. 2010. Changes in Snowfall in the Southern Sierra Nevada of California Since 1916. Energy & Environment, Vol. 21, No. 3, 2010
Full text [here]
Selected excerpts:
Abstract
A time series (1916–2009) of annual snowfall totals for Huntington Lake (HL, elev. 2141 m) in the southern Sierra Nevada of California is reconstructed. A reconstruction is (a) necessary because HL data after 1972 are mostly missing and (b) possible because nearby stations reveal high correlations with HL, two above 0.90. The results show mean annual snowfall in HL is 624 cm with an insignificant trend of +0.5 cm (+0.08%) ±13.1 cm per decade. Similar positive but insignificant trends for spring snowfall were also calculated. Annual stream flow and precipitation trends for the region again were insignificantly positive for the same period. Snow-water-equivalent comparisons, measured on 1 Apr since 1930 at 26 sites and since 1950 at 45, show similar small, mostly positive, and insignificant trends. These results combined with published temperature time series, which also reveal no significant trends, form a consistent picture of no remarkable long-term changes in the snowfall of this area and elevation of the southern Sierra Nevada of California since the early 20th century.
Conclusion
With the available data from six mid-elevation stations in the Southern Sierra region of California we reconstructed annual snowfall totals for 36 missing years of the Huntington Lake record to complete the time series (1916–2009). The standard error of the missing years is calculated to be ±36 cm, or 6% of the 94-year annual mean of 624 cm in the most robust estimation method (though we utilized the average of six methods which reduces the standard error further.)
The results of both the annual and spring snowfall time series indicate no remarkable changes for the 1916–2009 period in the basins drained by the Merced, San Joaquin, Kings and Kaweah Rivers. In the six reconstructions the range of trend results varied only slightly from -0.3% to +0.6% per decade. With a consensus trend of only +0.5 cm (+0.08%) per decade ±13.1 cm per decade there is high confidence in the “no-significant-trend” result. The corroborating information on temperature trends (Christy et al. 2006), stream flow, precipitation and shorter period snow water equivalent trends presented here are consistent with “no-significant-trend” in So. Sierra snowfall near 2000m elevation since 1916.
The statistical properties of annual snowfall, and associated annual variables mentioned above, demonstrate the high level of variability in western precipitation. For example, calculating trends over short periods, such as in 25-year segments, produces a wide range of trends as low as -83.0 to +82.8 cm per decade with a median of +10.2 cm per decade and a most recent (1985–2009) value of +15.9 (+2.6%) cm per decade. This suggests that the impacts of interannual and interdecadal variations are to be considered of serious import in comparison with impacts of long-term trends which have been shown to be negligible in this region to this point. …
Empirical Evidence for a Celestial Origin of the Climate Oscillations and Its Implications
Nicola Scafetta. 2010. Empirical Evidence for a Celestial Origin of the Climate Oscillations and Its Implications. Journal of Atmospheric and Solar-Terrestrial Physics(2010),doi:10.1016/j.jastp.2010.04.01
Full text [here]
Selected excerpts:
Abstract
We investigate whether or not the decadal and multi-decadal climateoscillations have an astronomical origin. Several global surface temperature records since 1850 and records deduced from the orbits of the planets present very similar power spectra. Eleven frequencies with period between 5 and 100 years closely correspond in the two records. Among them, large climate oscillations with peak-to-trough amplitude of about 0.1 and 0.25ºC, and periods of about 20 and 60 years, respectively, are synchronized to the orbital periods of Jupiter and Saturn. Schwabe and Hale solar cycles are also visible in the temperature records. A 9.1-year cycle is synchronized to the Moon’s orbital cycles. A phenomenological model based on these astronomical cycles can be used to well reconstruct the temperature oscillations since 1850 and to make partial forecasts for the 21st century. It is found that at least 60% of the global warming observed since 1970 has been induced by the combined effect of the above natural climate oscillations. The partial forecast indicates that climate may stabilize or cool until 2030–2040. Possible physical mechanisms are qualitatively discussed with an emphasis on the phenomenon of collective synchronization of coupled oscillators.
Conclusion
On secular, millenarian and larger time scales astronomical oscillations and solar changes drive climate variations. Shaviv’s theory (2003) can explain the large 145 Myr climate oscillations during the last 600 million years. Milankovic’s theory(1941) can explain the multi-millennial climate oscillations observed during the last 1000 kyr. Climate oscillations with periods of 2500, 1500, and 1000 years during the last 10,000 years (the Holocene) are correlated to equivalent solar cycles that caused the Minoan, Roman, Medieval and Modern warm periods(Bond etal.,2001; Kerr, 2001). Finally, several other authors found tha multi-secular solar oscillations caused bi-secular little ice ages (for example: the Sporer, Maunder, Dalton minima) during the last 1000 years (for example: Eddy, 1976; Eichler et al.,2009; Scafetta and West, 2007; Scafetta, 2009,2010).
Herein, we have found empirical evidences that the climate oscillations within the secular scale are very likely driven by astronomical cycles, too. Cycles with periods of 10–11, 12, 15, 20–22, 30 and 60 years are present in all major surface temperature records since 1850, and can be easily linked to the orbits of Jupiter and Saturn. The 11 and 22-year cycles are the well-known Schwabe and Hale solar cycles. Other faster cycles with periods between 5 and 10 years are in common between the temperature records and the astronomical cycles. Long-term lunar cycles induce a 9.1-year cycle in the temperature records and probably other cycles, including an 18.6-year cycle in some regions (McKinnell and Crawford, 2007). A quasi-60 year cycle has been found in numerous multi-secular climatic records, and it is even present in the traditional Chinese, Tibetan and Tamil calendars, which are arranged in major 60-year cycles. …
The existence of a 60-year natural cycle in the climate system, which is clearly proven in multiple studies and herein in Figs. 2, 6, 10 and 12, indicates that the AGWT promoted by the IPCC (2007), which claims that 100% of the global warming observed since 1970 is anthropogenic,is erroneous. In fact, since 1970 a global warming of about 0.5ºC has been observed. However, from 1970 to 2000 the 60-year natural cycle was in the warming phase and has contributed no less than 0.3ºC of the observed 0.5ºC warming, as Fig. 10B shows. Thus, at least 60% of the observed warming since 1970 has been naturally induced. This leaves less than 40% of the observed warming to human emissions. Consequently, the current climate models, by failing to simulate the observed quasi-60 year temperature cycle, have significantly over estimated the climate sensitivity to anthropogenic GHG emissions by likely a factor of three. …
The Anthropogenic Greenhouse Era Began Thousands of Years Ago
William F. Ruddiman. 2003. The Anthropogenic Greenhouse Era Began Thousands of Years Ago. Climatic Change 61: 261–293.
Full text [here]
Selected excerpts:
Abstract
The anthropogenic era is generally thought to have begun 150 to 200 years ago, when the industrial revolution began producing CO2 and CH4 at rates sufficient to alter their compositions in the atmosphere. A different hypothesis is posed here: anthropogenic emissions of these gases first altered atmospheric concentrations thousands of years ago. This hypothesis is based on three arguments. (1) Cyclic variations in CO2 and CH4 driven by Earth-orbital changes during the last 350,000 years predict decreases throughout the Holocene, but the CO2 trend began an anomalous increase 8000 years ago, and the CH4 trend did so 5000 years ago. (2) Published explanations for these mid- to late-Holocene gas increases based on natural forcing can be rejected based on paleoclimatic evidence. (3) A wide array of archeological, cultural, historical and geologic evidence points to viable explanations tied to anthropogenic changes resulting from early agriculture in Eurasia, including the start of forest clearance by 8000 years ago and of rice irrigation by 5000 years ago. In recent millennia, the estimated warming caused by these early gas emissions reached a global-mean value of ~0.8ºC and roughly 2ºC at high latitudes, large enough to have stopped a glaciation of northeastern Canada predicted by two kinds of climatic models. CO2 oscillations of ~10 ppm in the last 1000 years are too large to be explained by external (solar-volcanic) forcing, but they can be explained by outbreaks of bubonic plague that caused historically documented farm abandonment in western Eurasia. Forest regrowth on abandoned farms sequestered enough carbon to account for the observed CO2 decreases. Plague-driven CO2 changes were also a significant causal factor in temperature changes during the Little Ice Age (1300–1900 AD).
Introduction
Crutzen and Stoermer (2000) called the time during which industrial-era human activities have altered greenhouse gas concentrations in the atmosphere (and thereby affected Earth’s climate) the “Anthropocene”. They placed its start at 1800 A.D., the time of the first slow increases of atmospheric CO2 and CH4 concentrations above previous longer-term values. Implicit in this view is a negligible human influence on gas concentrations and Earth’s climate before 1800 AD.
The hypothesis advanced here is that the Anthropocene actually began thousands of years ago as a result of the discovery of agriculture and subsequent technological innovations in the practice of farming. This alternate view draws on two lines of evidence. First, the orbitally controlled variations in CO2 and CH4 concentrations that had previously prevailed for several hundred thousand years fail to explain the anomalous gas trends that developed in the middle and late Holocene.
Second, evidence from palynology, archeology, geology, history, and cultural anthropology shows that human alterations of Eurasian landscapes began at a small scale during the late stone age 8000 to 6000 years ago and then grew much larger during the subsequent bronze and iron ages. The initiation and intensification of these human impacts coincide with, and provide a plausible explanation for, the
divergence of the ice-core CO2 and and CH4 concentrations from the natural trends
predicted by Earth-orbital changes.
