Forests Fighting Climate

The rise of populations and technological and social development has driven up global demands for bio fuels and grain as feed for animals for meat. This creates powerful incentives for agro-industries to expand into forest regions, notably the Amazon rainforest, causing dramatic and often irreversible change to the environment (Nepstad et al. 2008). Forest fires, drought and logging increase susceptibility to further burning while deforestation and smoke can inhibit rainfall, exacerbating fire risk in this positive feedback loop. If sea surface temperature anomalies and associated droughts to continue, approximately 55% of the forests of the Amazon will be cleared, logged, damaged by drought or burned over the next 20 years, as shown in Figure 1 (Nepstad et al. 2008). The trees of the Amazon contain 90–140 billion tons of carbon, equivalent to approximately 9–14 decades of current global human-induced carbon emissions each year (Canadell et al. 2007). A lot of this is released back to the atmosphere, partly by a reduction in carbon uptake by the trees, but also in burning and soil process changes. Lenton et al. (2008) predict a timescale of 50 years for the Amazon to switch to an alternative state with severely decreased biodiversity and rainfall. A large fraction of precipitation in the Amazon basin is recycled, and reductions in precipitation lead to  lengthening of the dry season, and increases in summer temperatures that make it forest re-establishment difficult, and suggest the system may exhibit bi-stability, with two stable states (Lenton et al. 2008).

Figure 1 - Amazon forest degradation map (Nepstad et al., 2008)

It is also proposed that human induced climate change is impacting boreal forests, as shown by a study in the western United States that links forest “greenness” to fluctuating year-to-year snow-pack. This study showed that mid-elevation - those between approximately 6,500 to 8,000 feet - mountain ecosystems are most sensitive to rising temperatures and changes in precipitation and snow-melt (Trujillo et al, 2012). The study by University of Colorado, funded by NASA, used satellite and ground data to identify the threshold where mid-elevation forests sustained primarily by moisture shift into higher-elevation forests sustained primarily by sunlight and temperature. They found that  mid-elevation forests are very sensitive to snow that fell the previous winter, with about half of the mid-elevation forest greenness attributed to the previous winter’s snow accumulation (Trujillo et al, 2012). Climate studies indicate that snow-pack in mid-elevation forests in the Western United States and in similar forests around the world has been decreasing in the past 50 years due to regional warming (Trujillo et al., 2012), producing a feedback system that will continue to increase warming due to decreased albedo and reduced carbon sequestration. Lenton et al. (2008) predict that the decline of boreal forest would cause a biome switch on a scale of about 50 years, transitioning to open woodlands or grasslands. Under climate change the complex interaction between tree physiology, permafrost, and fire would experience increased water stress, increased peak summer heat stress causing increased mortality, vulnerability to disease and subsequent fire, as well as decreased reproduction rates (Lenton et al., 2008)

Nepstad et al (2008) conclude that trends in Amazon economies, forests and climate may lead to the replacement or severe degradation of more than half of the Amazon basin forests by 2030. They suggest that recent success in changing landholder behaviour, as well as the designation of protected areas and practical techniques for concentrating livestock production on smaller areas of land that could reduce the likelihood of severe environmental change.

Canadell, J. G. et al. (2007) “Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks”. Proc. Nat. Acad. Sci. USA 104, 18 866–18 870.

Lenton, T., M., H. Held, E. Kriegler, J. W. Hall, W. Lucht, S. Rahmstorf, and H. J. Schellnhuber, (2008) “Tipping elements in the Earth’s climate system” PNAS, 105, 6, 1786–1793

Nepstad, D., C., C. M. Stickler, B. Soares-Filho, and F. Merry. (2008) Interactions among Amazon land use, forests and climate: prospects for a near-term forest tipping point. Phil. Trans. R. Soc. B 363, 1737–1746

Trujillo, E., N. P. Molotch, M. L. Goulden, A. E. Kelly and R.C. Bales (2012) “Elevation-dependent influence of snow accumulation on forest greening” Nature Geoscience, 5, 705–709

Five Global Warming "Tipping Points"

This National Geographic article looks at 5 localities that are likely to change when we reach a tipping point relevant to that system, where crossing it would cause serious changes in some of Earth's system processes with knock-on effects on others. 

http://news.nationalgeographic.com/news/2009/03/photogalleries/tipping-points-climate-change/index.html 

Firstly, the Amazon Basin, where climate shifts may lead to less rainfall,huge loss of species diversity which would damage the forest's regulation of air quality, fresh water cycle, and atmospheric circulation.

Secondly, disruption on the Atlantic Meridional overturning circulation, preventing warm water from moving north and having a dramatic impact on ocean and terrestrial ecosystems, as well as affecting global climatic circulation.

Thirdly, a warming of 4 degrees C would cause massive melting of the Greenland ice sheet. An ice-free Greenland would cause up to 6 to 7 meters of sea-level rise, threatening up to 300 million people, as well as ecosystems, with harmful floods.

Fourth, some have suggested that the El Nino periodic shift in condition of the ocean and atmosphere in the tropical Pacific may become an almost permanent state, causing severe drought in Southeast Asia and the Amazon Basin and increased floods and changes in the marine food web along the South American Pacific coast.

Fifth, melting Antarctic ice could raise raise the world's sea level by up to 6 to 7 meters. The melting ice may reveal islands under the ice that are currently buried. Already fast moving ice streams have released large amounts of freshwater into surrounding oceans.

James Hansen - speaking truth to power

James Hansen: activist, environmentalist, physicist, astronomer, scientist. Whichever of these you choose, he’s a man recognized for “speaking truth to power”, that truly cares about Earth’s climate. His extensive work on climate research and on educating governments and public alike has raised awareness of global climate change significantly in the last 30 years.

 

For his TED talk in 2012, “James Hansen: Why I must speak out about climate change”, we see your average American man humbly and wholeheartedly addressing his audience.  He’s of mid-height, greying, and wearing the same hat as the day he was arrested for protesting outside the White House, but then again “What would you do if you knew what I (Hansen) know?”.

 He started his early work with Professor Van Allen, moving to NASA on a project studying Venus’s climate. It was during this project that Hansen turned this knowledge to Earth, truly adopting NASA’s mission statement: “TO UNDERSTAND AND PROTECT THE HOME PLANET” (a sentence quietly removed in 2006). He made calculations of the greenhouse effect and its predicted impact as atmospheric composition persistently changed.  His groundbreaking 1981 paper in Science magazine, observed warming of 0.4°C consistent with CO2 increase. They predicted that warming would exceed noise level of random weather by 21^st C, causing shifting climate zones, drought and flood prone areas, rising sea levels, erosion of ice sheets, opening of the North West Passage…all of which are well underway. Following this paper, Hansen testified to congress, emphasizing increase in climate extremes around globe, with stronger extreme events 3sd or more above the norm. The paper stated “CO2 effects on climate may make full exploitation of coal resources undesirable”, a statement ignored by the Presidents climate task force, with which Hansen spoke twice.

 

Throughout the TEDtalk, Hansen makes the alarming science easy to understand...“The extra energy earth gains each day is 20x the energy used by all of humanity, its 400 000 Hiroshima bombs per day, all year”, and (especially for the Americans) “A warmer ocean releases CO2, just as a warm Coca-Cola does.”

 

The upper half of ocean is gaining heat at substantial rate, with the deep ocean not far behind and land warming to 10’s meters depth. This path guarantees that we will pass tipping points – ice sheet disintegration, 15-20% species committed to extinction by 2100, increasing floods and drought intensity leading to famine and global economic decline, and the longer we wait, the more difficult and expensive it becomes to prevent and reduce this.

The science is clear, Hansen concludes, with a plea to all “Clearly I haven’t gotten this message across. I need your help. We owe it to our children and grandchildren”. 

Have a listen yourself, if you weren't convinced on the severity of climate change already, this talk might provide your tipping point.