The world is now meeting in Poland to tackle global warming – and Earthjustice is there. Read our daily dispatches.

The Federated States of Micronesia, one of the leading voices of the Alliance of Small Island States – countries whose very existence are threatened by global warming-induced sea level rise – has called on the governments assembled in Poznan to take urgent action in light of potential catastrophic tipping points in the Earth’s climate system.

A "tipping point" describes an abrupt, non-linear, and irreversible change – a critical threshold at which a small additional change can forever alter the planet’s climate system and make any human reversal of the change impossible. The proverbial straw that breaks the camel’s back. Examples you’ve probably heard about include the potential collapse of ocean currents that maintain the Earth’s weather patterns; a massive "die back" of the Amazon rainforest due to drought and wildfires; and the melting of Arctic sea ice and the Greenland ice sheet leading to catastrophic sea level rise.

Martin and I have been collaborating with colleagues from the Arctic to the Amazon to advocate for rapid action to reduce emissions of black carbon, now widely thought to be one of the most effective fast-track mitigation strategies to slow global and Arctic warming in the near term, avoid catastrophic Arctic tipping points, and buy time for implementation of the critical strategies to cut long-lived greenhouse gas emissions that are the subject of these UN climate negotiations.

Black carbon has been described as CO2’s partner in crime. It is a conventional air pollutant – a component of soot, the fine particulate matter that spews from diesel trucks and buses – that is a leading cause of asthma, other respiratory diseases and cancers in the US and around the world. It is also a critical climate warming agent both in the atmosphere and when deposited on snow and ice (in the Arctic, the Andes or Glacier National Park) where it speeds melting by absorbing sunlight and reducing surface reflectivity. James Hansen, NASA’s top climate scientist, has estimated that black carbon "may be responsible for a quarter of observed global warming."

Arctic summer sea ice shrank to it’s smallest extent in recorded history in 2007 – an area approximately equal to the size of Alaska and Texas combined melted away; 2008 saw a record low in sea ice volume.  As Al Gore told the world in his Nobel prize acceptance speech last year, the North Polar ice cap is "falling off a cliff," making it "harder and harder to misinterpret the signs that our world is spinning out of kilter." Scientists are now predicting that the Arctic ocean may be ice-free in summer by 2011-2015, eighty years ahead of the "consensus" predictions made by the Intergovernmental Panel on Climate Change (IPCC).

Earthjustice is taking a two-track approach to protect the extraordinary cultures, ecosystems and biodiversity in the Arctic. We’re working for a precautionary approach to the rapidly increasing industrial activity in areas newly accessible because of Arctic ice melt. And we’re advocating for fast-track action to reduce emissions of short-lived climate warming pollutants like black carbon both in the US and around the world. Together these strategies may be he best hope for slowing Arctic warming and giving the extraordinary cultures, biodiversity and ecosystems of the region time to adapt to the warming that is already in the "pipeline" due to past and future emissions of long-lived greenhouse gases like CO2. And slowing Arctic warming now is absolutely essential to avert catastrophic tipping points such as permafrost melt and resulting methane release, and the melting of the Greenland ice sheet and resulting sea level rise.

Two side events (brief thematic meetings outside of the negotiations) held in Poznan highlighted the urgent need for rapid action to avoid Arctic tipping points. The first, convened by the Norwegian government on behalf of the Arctic Council (an intergovernmental science and policy forum for Arctic governments and peoples) focused on the work to analyze rapid action measures that the eight Arctic countries could take to reduce emissions of "short-lived" climate agents such as methane, tropospheric ozone and black carbon. (Earthjustice is advocating for Arctic nations to implement a Northern Hemisphere black carbon reduction strategy.)

The second side event, organized by the US-based Institute for Governance and Sustainable Development, featured Dr. Herman Held of the Potsdam Institute for Climate Impact Research in Germany. Echoing the title of his recently published article Tipping elements in the Earth’s climate system, he warned that "greatest threats are tipping the Arctic sea-ice and the Greenland ice sheet," stressing that ice melt is being vastly underestimated, and that non-linear abrupt climate change is not being taken into account as it should be by the climate convention.

Of course, we’ve been warned before. As James Hansen wrote in 2005: "The greatest threat of climate change for human beings, I believe, lies in the potential destabilization of the massive ice sheets in Greenland and Antarctica. As with the extinction of species, the disintegration of ice sheets is irreversible for practical purposes. Our children, grandchildren, and many more generations will bear the consequences of choices that we make in the next few years."