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.

Planetary Boundaries and Tipping Points explained!

If you do any reading about "tipping points" you'll be bombarded with things like 'planetary boundaries', 'regime shifts', 'critical transitions' and just about every combination of these words. It can be a bit confusing! So I'm going to explain it in what I hope is a much clearer way....

Brook et al. (2013) describe the following:

· Planetary boundary: a concept developed to define a desired operating range for Earth-system features and processes. Crossing a boundary implies damage or loss of existing functions or services across the system.

· Regime shift: a large, relatively rapid reorganization of the state of an ecosystem that can be triggered by synergistic feedbacks. Regime shifts can result from crossing tipping points, and are often hard to anticipate and difficult to reverse.

· Tipping point: the critical point at which strong non-linearities appear in the relationship between ecosystem attributes and drivers; once a tipping point threshold is crossed, the change to a new state is typically rapid and might be irreversible or exhibit hysteresis.

Life on Earth has displayed abrupt and massive changes in the past, so we have no reason to expect that similar global regime shifts will not occur again. These shifts changed ecosystem dynamics worldwide by rising temperatures, changes in rainfall, retreat of polar ice and glaciers, and declining ocean pH amongst others, resulting in profound changes in ecosystem services, biodiversity, and aesthetic values. (Hughes et al. 2013). 

The problem is, not all these planetary boundaries and tipping points have been defined, and crossing these thresholds is unlikely to manifest as sudden and simultaneous collapses worldwide.What if we've already passed unrecognized and unanticipated tipping points as incremental changes accumulate, and are in a slow transition to a new regime? Once a transition occurs, it can be difficult or even impossible to return to the previous state (Barnosky et al, 2012).

This image from Barnosky et al (2012) shows a prediction of Earth ecosystem response as human population grows as does its impact on the environment. Here, the system crosses a tipping point and reaching an alternative stable state.

Human forcing includes transformation of 43% of land to agricultural or urban landscapes, with the remainder of natural landscapes broken up by roads. Even during the last global-scale critical transition, only 30% of Earth’s surface went from being covered by glacial ice to being ice free! Modelling suggests that for a third of Earth, plant species will not be able to migrate quick enough to keep up with climate change, and those that can will have to battle highly fragmented landscapes (Barnosky et al. 2012).

The scientific concept and potential policy implications of tipping points and their consequences have recently attracted considerable interest (Brook et al, 2013) and rightly so. Looking at past global-scale state shifts and the global forcings we continue to exert, suggests that another global-scale state shift is isn't far away, if it has not already begun (Barnosky et al, 2012). The extent and scale of human–biosphere interactions and disruption highlights the need to operate within safe planetary boundaries say Hughes et al, (2013). Regardless, we must address causes of human-driven global change and improve our management of the environment in order to prevent a global-scale state shift, or at least to monitor it as much as possible.

• Barnosky, A., D., Et Al. (2012) “Approaching a state shift in Earth’s Biosphere” Nature, 486, 52-58
• Brook, B.W. et al. (2013) Does the terrestrial biosphere have planetary tipping points? Trends Ecol. Evol. 28, 396–401
• Hughes, T., P., S. Carpenter, J. Rockstrom, M. Scheffer, and B. Walker (2013) “Multiscale regime shifts and planetary boundaries” Trends in Ecology & Evolution , 28, 7

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.

Pointing to the big picture.

Tasked with keeping a blog for 3 months for my 3rd year module in Global Environmental Change at UCL, I came home with a world of ideas. I told my boyfriend that I'd decided to write about climate tipping points. 

That's great, he said…what are “tipping points”? 

At this I paused, gave a vague description with a few strange analogies about burning your toast, and silently vowed to find a some good articles that would categorically sum up tipping points, for me and for my audience. 

Now, this proved much more difficult than expected. Although I knew about tipping points in Earth’s climate system, I had never considered that they existed elsewhere. As it turns out, ANYTHING that is in the slightest bit dynamic has a so called “tipping point”: fashion, make-up, the economy, sport, there’s even a Tipping Points game show in which contestants play with a giant arcade-style coin pusher (yes I watched it . . . it’s nail-biting). What shocked me most was that climate tipping points didn't dominate the primitive Google search, despite potentially being one of the most daunting and difficult factors in global climate change past, present and future.

TIPPING POINTS are thresholds beyond which dramatic changes in conditions with considerable and largely unpredictable consequences occur. It only takes a small change to make a huge difference; Lenton says “A climate ‘tipping point’ occurs when a small change in forcing triggers a strongly nonlinear response . . . qualitatively changing its future state”. They've happened before, pushing the Earth in and out of Ice Ages, but these have all been natural, caused by solar variability and a chain of events, such as melting permafrost and icesheets. This time, the Anthropocene threatens a new era of climate change, comparable with previous global mass extinctions. The editorial from Nature Climate Change Vol. 1 says “An early warning of Earth tipping points will bring us closer to staving off abrupt climate change, but a societal tipping point is needed to achieve sustainability”. 

Tipping points MUST be considered by policy makers, scientists and the general public worldwide in order for the issue to be addressed and acted upon.

Image from xkcd.com, source of data for image Dyke, A. et al, 2002. "The Laurentide and Innuitian Ice Sheets During the Last Glacial Maximum"