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Climate Change 

September 27, 2013

New IPCC report

IPCC 2013 report

The IPCC’s new summary report has been released: “Climate Change 2013. The physical science basis“. The publication is available for free downloading or online reading. Probably the most significant conclusion of the study is that scientists are 95% certain that human activity is responsible for the ongoing episode of recent global warming. The details of the document cover the mechanics of greenhouse gas-driven warming given updated emissions data, and the physical consequences, including warming air temperatures, changes in precipitation (mostly rainfall), sea level rise, and other ocean changes. The report also explores predicted changes to biogeochemical cycles, the all-important pathways through which living systems interact with, influence and are influenced-by the physical and chemical environments.

So now the real work begins in a sense. Given this state-of-the-art report, it will now be up to biologists, economists, sociologists, policy makers and others to translate these findings and predictions of the physical world into impacts on the living world, including our human society. These will be challenging efforts, but necessary if we are to then move onto the next steps of formulating solutions, both mitigative and adaptive. Further down the road, and of particular personal scientific interest, will be studies to figure out how changes to the living world, both naturally driven and perhaps also based on human decisions, will feed back into the physical world. The work never ends!

Here’s a nice summary and commentary from the BBC: “IPCC climate report: humans ‘dominant cause’ of warming“.


Filed under: Climate Change — Peter @ 6:58 am

September 21, 2013

Overpopulation? No problem!

Giving Out Corn to the People, During a Season of Scarcity.”: Chinese officials engaged in famine relief. Detail of engraving by G. F. Sargent.

I recently wrote a commentary on Erle Ellis’ op-ed in the NY Times, addressing human overpopulation, food, and ecosystems. I found it to be a rather poorly constructed article, and addressed it in my Food Weblog. Here is the full response:
Overpopulation? No Problem!


Filed under: Climate Change — Peter @ 10:29 pm

September 3, 2013

Tipping the Biosphere Part III: A Tipping Point for Earth?

This is the third installment of my essay, Tipping the Biosphere.
Part II.
 

(Image by Cheng (Lily) Li)


“Tipping point” has become a part of modern jargon, referring to a sudden change in the state of a system (e.g. an explosive disease outbreak) in response to an external driving force (or “control parameter” in scientific jargon). There is a considerable body of mathematics underlying this jargon, and we can identify four key features of systems that possess tipping points. First, the driving force can be applied incrementally over a broad range of intensities and result in little change to the system. This can be caused by a natural resistance of the system to change, or resiliency so that after being disturbed the system returns to its pre-disturbance state. Second, there is a point at which the next incremental change of the controlling parameter results in a significant change in the system’s state. The straw has broken the camel’s back and the system “tipped”. Response to the driving force changed either because the intensity of the driver can now overcome the internal resistance or resiliency of the system, or had eroded it incrementally, setting in motion previously inert or insignificant processes. Alternatively, the intensity of the driver can be reduced to a point where internal processes become more effective controllers, rendering the driver ineffective. Third, the intensity of the disturbance at which the system tips differs according to whether intensity is increasing or decreasing. In other words, if you added 10 kg to tip your scale, you would have to remove more than 10 kg to regain balance! Finally, two similar states can nevertheless be divergent in their responses, i.e. are sensitive to initial conditions.

Tipping points in many physical systems are well understood and find application in physics and engineering. In other real-life situations with apparent tipping points, however, such as disease outbreaks, or socio-political upheavals, analysis is more difficult. Difficulties stem from an incomplete identification and understanding of the driving factors, limits on the precision with which those factors can be measured, and complex interactions among multiple drivers and the system’s state. Therefore, when change occurs, it often surprises.

Why then do some scientists argue that the biosphere is approaching a tipping point? Specifically, why identify population size and resource consumption as controlling parameters? Because the effective drivers that result from those parameters, e.g. climate change and ecosystem disruption, have caused biosphere transitions in the past, and are themselves capable of dramatic transitions. For example, there is considerable concern that the consequences of ongoing global warming will be manifested as sudden shifts in climatic regimes rather than gradual transitions[7]. Climate change in the geologic past altered the biosphere in diverse ways, including extinctions and outbursts of evolutionary diversification. Another agent of ancient biosphere transformation was planetary or ecosystem primary productivity. Primary productivity is the energy converted to food by plants and other photosynthesizers. Large increases of primary production in the past, fertilized by various processes such as volcanism, were associated with increases of biological richness and ecological diversity. Large disruptions or decreases of this energy supply, however, linked to events such as asteroid impacts, climate change and oceanographic changes, are associated with regional to global ecological collapses and extinctions[8]. Humans today utilize or influence 24-41% of global primary production through the agricultural cultivation of a rather low diversity of species and the direct utilization or alteration of productive terrestrial systems[9,10]. In the oceans, where microscopic organisms are responsible for up to 50% of the Earth’s primary production, there is growing concern about the effects of increasing ocean temperatures and acidity. More directly, when we reduce the amount of space available to species or biological communities, or reduce the connectivity among those spaces, the result is extinction or community collapse. Thus, despite difficulties inherent to predicting tipping points in a system as complex as the global biosphere, there is sufficient evidence at both long time scales and small spatial scales that the biosphere is capable of such transitions, and sufficient reason to be concerned. An important question then is, as we increase the amount of the biosphere affected by humans, will local and regional collapses interact synergistically to result in global collapse? Counterintuitively, potential solutions emerge when we acknowledge the fundamental roles of human population size and resource consumption.
 
[7] Lenton, T. M. et al. 2008. Tipping elements in the Earth’s climate system. Proceedings of the National Academy of Sciences, 105: 1786-1793.
[8] Roopnarine, P. D. 2006. Extinction cascades and catastrophe in ancient food webs. Paleobiology, 32: 1-19.
[9] Haberl, H. et al. 2007. Quantifying and mapping the human appropriation of net primary production in Earth’s terrestrial ecosystems. Proceedings of the National Academy of Sciences, 104: 12942-12947.
[10] Roopnarine, P. D. 2008. Ecological Informatics: Catastrophe Theory. Encyclopedia of Ecology, Elsevier Press. p. 531-536.


Filed under: Climate Change — Peter @ 9:02 pm

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