AGW Observer

Observations of anthropogenic global warming

Papers on pre-industrial anthropogenic climate forcing

Posted by Ari Jokimäki on October 26, 2010

This is a list of papers on the effect of pre-industrial mankind to the climate. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

Contribution of anthropogenic land cover change emissions to preindustrial atmospheric CO2 – Reick et al. (2010) “Based on a recent reconstruction of anthropogenic land cover change (ALCC) we derive the associated CO2 emissions since 800 AD by two independent methods: a bookkeeping approach and a process model. The results are compared with the preindustrial development of atmospheric CO2 known from antarctic ice cores. Our results show that preindustrial CO2 emissions from ALCC have been relevant for the preindustrial carbon cycle, although before 1750 AD their trace in atmospheric CO2 is obscured by other processes of similar magnitude. After 1750 AD the situation is different: the steep increase in atmospheric CO2 until 1850 AD – this is before fossil-fuel emissions rose to significant values – is to a substantial part explained by growing emissions from ALCC.”

Biophysical feedbacks between the Pleistocene megafauna extinction and climate: The first human-induced global warming? – Doughty et al. (2010) “A large increase in Betula during a narrow 1000 year window, ∼13,800 years before present (YBP) in Alaska and Yukon corresponded in time with the extinction of mammoths and the arrival of humans. Pollen data indicate the increase in Betula during this time was widespread across Siberia and Beringia. We hypothesize that Betula increased due to a combination of a warming climate and reduced herbivory following the extinction of the Pleistocene mega herbivores. The rapid increase in Betula modified land surface albedo which climate-model simulations indicate would cause an average net warming of ∼0.021°C per percent increase in high latitude (53–73°N) Betula cover. We hypothesize that the extinction of mammoths increased Betula cover, which would have warmed Siberia and Beringia by on average 0.2°C, but regionally by up to 1°C. If humans were partially responsible for the extinction of the mammoths, then human influences on global climate predate the origin of agriculture.”

The prehistoric and preindustrial deforestation of Europe – Kaplan et al. (2009) “Humans have transformed Europe’s landscapes since the establishment of the first agricultural societies in the mid-Holocene. The most important anthropogenic alteration of the natural environment was the clearing of forests to establish cropland and pasture, and the exploitation of forests for fuel wood and construction materials. While the archaeological and paleoecological record documents the time history of anthropogenic deforestation at numerous individual sites, to study the effect that prehistoric and preindustrial deforestation had on continental-scale carbon and water cycles we require spatially explicit maps of changing forest cover through time. Previous attempts to map preindustrial anthropogenic land use and land cover change addressed only the recent past, or relied on simplistic extrapolations of present day land use patterns to past conditions. In this study we created a very high resolution, annually resolved time series of anthropogenic deforestation in Europe over the past three millennia by 1) digitizing and synthesizing a database of population history for Europe and surrounding areas, 2) developing a model to simulate anthropogenic deforestation based on population density that handles technological progress, and 3) applying the database and model to a gridded dataset of land suitability for agriculture and pasture to simulate spatial and temporal trends in anthropogenic deforestation. Our model results provide reasonable estimations of deforestation in Europe when compared to historical accounts. We simulate extensive European deforestation at 1000 BC, implying that past attempts to quantify anthropogenic perturbation of the Holocene carbon cycle may have greatly underestimated early human impact on the climate system.” Jed O. Kaplan, Kristen M. Krumhardt, and Niklaus Zimmermann, The prehistoric and preindustrial deforestation of Europe, Quaternary Science Reviews, Volume 28, Issues 27-28, December 2009, Pages 3016-3034, doi:10.1016/j.quascirev.2009.09.028. [Full text]

Effects of human land-use on the global carbon cycle during the last 6,000 years – Olofsson & Hickler (2008) “Humanity has become a major player within the Earth system, particularly by transforming large parts of the land surface and by altering the gaseous composition of the atmosphere. Deforestation for agricultural purposes started thousands of years ago and might have resulted in a detectable human influence on climate much earlier than the industrial revolution. This study presents a first attempt to estimate the impact of human land-use on the global carbon cycle over the last 6,000 years. A global gridded data set for the spread of permanent and non-permanent agriculture over this time period was developed and integrated within the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). The model was run with and without human land-use, and the difference in terrestrial carbon storage was calculated as an estimate of anthropogenic carbon release to the atmosphere. The modelled total carbon release during the industrial period (a.d. 1850–1990) was 148 gigatons of carbon (GtC), of which 33 GtC originated from non-permanent agriculture. For pre-industrial times (4000 b.c.–a.d. 1850), the net carbon release was 79 GtC from permanent agriculture with an additional 35 GtC from non-permanent agriculture. The modelled pre-industrial carbon release was considerably lower than would be required for a substantial influence on the climate system.” Jörgen Olofsson and Thomas Hickler, Vegetation History and Archaeobotany, Volume 17, Number 5, 605-615, DOI: 10.1007/s00334-007-0126-6. [Full text]

Using multiple archives to understand past and present climate–human–environment interactions: the lake Erhai catchment, Yunnan Province, China – Dearing et al. (2008) “A 6.48 m sediment core sequence from Erhai lake, Yunnan Province, provides a multi-proxy record of Holocene environmental evolution and human activity in southwest China. These sedimentary records provide proxy time series for catchment vegetation, flooding, soil erosion, sediment sources and metal workings. They are complemented by independent regional climate time-series from speleothems, archaeological records of human habitation, and a detailed documented environmental history. The article attempts to integrate these data sources to provide a Holocene scale record of environmental change and human–environment interactions. These interactions are analysed in order to identify the roles of climate and social drivers on environmental change, and the lessons that may be learned about the future sustainability of the landscape. The main conclusions are: lake sediment evidence for human impacts from at least 7,500 cal year BP is supported by a terrestrial record of cultural horizons that may extend back to ∼9,000 cal year BP. A major shift in the pollen assemblage, defined by detrended correspondence analysis, at ∼4,800 cal year BP marks the transition from a ‘nature-dominated’ to a ‘human-dominated’ landscape. From 4,300 cal year BP, a change in river discharge responses may signal the beginning of hydraulic modification through drainage and irrigation. Major increases in disturbed land taxa and loss of forest taxa from 2,200 cal year BP onward, also associated with the start of significant topsoil erosion, register the expansion of agriculture by Han peoples. It is also the start of silver smelting linked to trade along the SW Silk Road with Dali becoming a regional centre. Peak levels of disturbed land taxa, topsoil and gully erosion are associated with the rise and fall of the Nanzhao (CE 738–902) and Dali (CE 937–1253) Kingdoms, and the documented environmental crisis that occurred in the late Ming and Qing dynasties (CE 1644–1911). The crisis coincides with a stronger summer monsoon, but exploitation of marginal agricultural land is the main driver. These historical perspectives provide insight into the resilience and sustainability of the modern agricultural system. The largest threat comes from high magnitude-low frequency flooding of lower dry farmed terraces and irrigated valley plains. A sustainable future depends on reducing the use of high altitude and steep slopes for grazing and cultivation, maintaining engineered flood defences and terraces, and anticipating the behaviour of the summer monsoon.” J. A. Dearing, R. T. Jones, J. Shen, X. Yang, J. F. Boyle, G. C. Foster, D. S. Crook and M. J. D. Elvin, Using multiple archives to understand past and present climate–human–environment interactions: the lake Erhai catchment, Yunnan Province, China, 2008, Journal of Paleolimnology, Volume 40, Number 1, 3-31, DOI: 10.1007/s10933-007-9182-2.

Climate-human-environment interactions: resolving our past – Dearing (2006) “The paper reviews how we can learn from the past about climate-human-environment interactions at the present time, and in the future. It focuses on data sources for environmental change at local/regional and regional/global spatial scales, and shows the scope and limitations of each. It reviews alternative methods for learning from the past, including the increasing use of simulation models. The use of multiple records (observational, palaeoenvironmental, archaeological, documentary) in local case-studies is exemplified in a study from China, where independent records help unravel the complexity of interactions and provide a basis for assessing the resilience and sustainability of the landscape system. Holocene global records for Natural Forcings (e.g. climate and tectonics), Human Society and Ecosystems are reviewed, and the problems of reconstructing global records of processes that are only recorded at local scales examined. Existing regional/global records are used to speculate about the veracity of anthropogenic forcing of global climate, with specific consideration of the Ruddiman theory. The paper concludes that a full understanding of causes of earth system change through (at least) the Holocene can come only through the most rigorous reconstructions of climate, human activities and earth processes, and importantly their interactions, at all locations and at all scales. It follows that we need to promote inter-scale learning: regionalisation and generalisation of existing data would be useful first steps. There is now a need to develop long-term simulation models that can help anticipate complex ecosystem behaviour and environmental processes in the face of global environmental change – and resolving our past is an essential element in that endeavour.” Dearing, J. A.: Climate-human-environment interactions: resolving our past, Clim. Past, 2, 187-203, doi:10.5194/cp-2-187-2006, 2006. [Full text]

The Anthropogenic Greenhouse Era Began Thousands of Years Ago – Ruddiman (2003) “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 ananomalous increase 8000 years ago, and the CH4 trend did so 5000 years ago.(2) Published explanations for these mid- to late-Holocene gas increases basedon 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 0.8 °C and roughly 2 °C 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 toolarge 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 CO2decreases. Plague-driven CO2 changes were also a significant causal factor in temperature changes during the Little Ice Age (1300–1900 AD).” William F. Ruddiman, Climatic Change, Volume 61, Number 3, 261-293, DOI: 10.1023/B:CLIM.0000004577.17928.fa. [Full text]

The case for human causes of increased atmospheric CH4 over the last 5000 years – Ruddiman & Thomson (2001) “We propose that humans significantly altered atmospheric CH4 levels after 5000 years BP and that anthropogenic inputs just prior to the industrial revolution accounted for up to 25% of the CH4 level of 725 ppb (parts per billion). We base this hypothesis on three arguments: (1) the 100 ppb increase in atmospheric CH4 that occurred after 5000 years BP follows a pattern unprecedented in any prior orbitally driven change in the ice-core record; (2) non-anthropogenic explanations for this increase (expansion of boreal peat lands or tropical wetlands) are inconsistent with existing evidence; and (3) inefficient early rice farming is a quantitatively plausible means of producing anomalously large CH4 inputs to the atmosphere prior to the industrial revolution. If the areas flooded for farming harbored abundant CH4-producing weeds, disproportionately large amounts of CH4 would have been produced in feeding relatively small pre-industrial populations.” [Full text]

On the origin and magnitude of pre-industrial anthropogenic CO2 and CH4 emissions – Kammen & Marino (1993) “The potential impact of human activity on the climate system, particularly as related to fossil fuel combustion, is widely acknowledged. However, little is known of the origin and magnitude of anthropogenic non-fossil emissions, although this activity currently contributes up to 40% of the global CO2 emissions. Here we provide estimates of CO2 and CH4 emissions resulting from pre-industrial societies by combining historical demographic and archaeological data. Combustion of non-fossil carbon for domestic needs, small-scale industrial/craft activities and resulting from agricultural land management was significant, reaching about 1 Gt of carbon (GtC) as CO2yr−1 and 10 Tg of of carbon CH4yr−1 by 1800 A.D. This data implies a significant anthropogenic source of pre-industrial atmospheric greenhouse gases; consistent with estimates derived from carbon cycle models. We illustrate the contribution of archaeological data with two case studies: (i) estimates of CH4 emissions from agricultural activity from the Maya Lowlands; and (ii) evidence of correlations between climatic and socio-economic conditions in North Atlantic Norse settlements. This work provides an improved baseline for studies of historic climate change, such as the Little Ice Age, as well as for evaluating strategies for mitigating current greenhouse gas emissions.”

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