Abrupt Climate Change
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The past climate change heats up PNAS 2000 research paper
Steven M. Stanley
Research has provided a shocking new assessment of the speed with which major climate changes can sweep across our planet.
The most precise evidence of rapid climate change comes from cores extracted from mountain glaciers and from the larger ice sheets of Greenland and Antarctica. Annual layers in the glacial ice provide the chronology and key data on snowfall, temperature, influx of dust, and trace gases from the ancient atmosphere trapped in air bubbles.
There is ominous evidence that, during the past few thousand years, Earth's climate has been anomalously tranquil compared to its behavior during the preceding hundred thousand years.
Ice-core evidence of abrupt climate changes
Richard B. Alley
Ice-core records show that climate changes in the past have been large, rapid, and synchronous over broad areas extending into low latitudes, with less variability over historical times. These ice-core records come from high mountain glaciers and the polar regions, including small ice caps and the large ice sheets of Greenland and Antarctica.
As the world slid into and out of the last ice age, the general cooling and warming trends were punctuated by abrupt changes. Climate shifts up to half as large as the entire difference between ice age and modern conditions occurred over hemispheric or broader regions in mere years to decades. Such abrupt changes have been absent during the few key millennia when agriculture and industry have arisen.
Abrupt climate change as defined by the The National Research Council is "an abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause" (NRC, 2002).
There is no question that today's abrupt accelerating atmospheric greenhouse gas levels have led to a dramatic obvious sustained abrupt accelerating radiative forcing (heating) of the biosphere. This is our most policy relevant definition of abrupt climate system change.
Ocean heating and acidification are abrupt and both still accelerating.
Abrupt Arctic change The Arctic is now heating up 3 x the global average, which is abrupt and causing adverse abrupt Arctic changes, making Arctic climate change abrupt by any definition.
The real question is do today's record high atmospheric GHGs have the world committed (locked in) to actual abrupt catastrophic impacts to the planet. There is evidence from amplifying feedback science that this is the case.
The most recent and dramatic example is the Younger Dryas 13,000 years ago, of abrupt cooling terminated by an abrupt warming of 10C in a only decade or two! The rapid warming is attributed to methane and CO2 from wetlands and thawing permafrost.
The IPCC AR5 : a large-scale change in the climate system that takes place over a few decades or less, persists (or is anticipated to persist) for at least a few decades, and causes substantial disruptions in human and natural systems. There is information on potential consequences of some abrupt changes
The planetary catastrophic risk of abrupt climate change has been recognized for many. In 2002 the us National Academy published Abrupt Climate Changes: Inevitable Surprises
- Examples of components susceptible to such abrupt change are the strength of the Atlantic Meridional Overturning Circulation (AMOC),
- clathrate methane release,
- tropical and boreal forest dieback,
- disappearance of summer sea ice in the Arctic Ocean,
- long-term drought and
- monsoonal circulation
A study of Earth’s climate history suggests the inevitability of “tipping points”— thresholds beyond which major and rapid changes occur when crossed—that lead to abrupt changes in the climate system. The history of climate on the planet—as read in archives such as tree rings, ocean sediments, and ice cores—is punctuated with large changes that occurred rapidly, over the course of decades to as little as a few years. There are many potential tipping points in nature, as described in this report, and many more that we humans create in our own systems. The current rate of carbon emissions is changing the climate system at an accelerating pace, making the
chances of crossing tipping points all the more likely.
The question is now whether the surprises can be anticipated, and the element of surprise reduced. That issue is addressed in this report.
The abrupt climate changes and abrupt climate impacts discussed here present substantial risks to society and nature. The ability to anticipate what would otherwise be “surprises” in the climate system requires careful monitoring of climate conditions, improved models for projecting changes, and the interpretation and synthesis of scientific data using novel analysis techniques. In light of the importance of actionable information about the occurrence and impacts of abrupt changes, it is the Committee’s judgment that action is urgently needed to improve society’s ability to anticipate abrupt climate changes and impacts.
To address these needs the Committee recommends development of an Abrupt Change Early Warning System (ACEWS). Surprises in the climate system are inevitable: an early warning system could allow for the prediction and possible mitigation of such changes before their societal impacts are severe. Identifying key vulnerabilities can help guide efforts to increase resiliency and avoid large damages from abrupt change in the climate system, or in abrupt impacts of gradual changes in the climate system, and facilitate more informed decisions on the proper balance between mitigation and adaptation. With adequate scientific monitoring and study of these potential changes to the climate system, the probability that society can anticipate future abrupt climate changes and impacts will be substantially increased.
12 Oct 20015 Catalogue of abrupt shifts in Intergovernmental Panel on Climate Change climate models. 'Eighteen out of 37 events occur for global warming levels of less than 2°'
The US under the Department of Energy has a special research project called the Investigation of the Magnitudes and Probabilities of Abrupt Climate TransitionS (IMPACTS) Project. It addresses four abrupt situations.
- Dynamics of ice shelf — ocean interaction and marine ice sheet instability;
- Boreal/Arctic-climate positive feedbacks and ACC;
- Rapid destabilization of methane hydrates in Arctic Ocean sediments;
- Mega droughts in North America, including the role of biosphere-atmosphere feedbacks.
It is quite a contradiction to expect unpredicted abrupt change to be somehow predictable, and even if we could predict an abrupt even by the very nature of abrupt climate change, there is nothing we could do about it.
The 2013 assessment has concluded that the threat from abrupt climate events this century is less than had previously been feared, but this relies on computer models and climate models inherently do not capture sudden non linear change.
Some abrupt changes that have been widely discussed in the literature because they were previously considered to be potential threats with poorly known probability. More recent research findings have shown that they may be less likely to occur within this century than previously considered possible. These include disruption to the Atlantic
Meridional Overturning Circulation (AMOC) and potential abrupt changes of high-latitude methane sources (permafrost soil carbon and ocean methane hydrates). Although the Committee judges the likelihood of an abrupt change within this century to be low for these processes, should they occur even next century or beyond, there would likely be severe impacts. Furthermore, gradual changes associated with these processes can still lead to
consequential changes. Thus, they merit further study.
CLIMATE SYSTEM EMERGENCY INSTITUTE
The Health and Human Rights Approach to Greenhouse Gas Pollution