Last night I sat down and skimmed through the 106pp report prepared by the prestiguous Postdam Institute for Climate Impact Research (PIK) for the World Bank. It is a shocking read, that we are presently on the business as usual emissions path of 4 degrees C (7.2°F) of global warming by about the 2060s and 6 degrees C (10.8°F) of warming by the turn of the century, just 88 years hence.

The International Energy Agency also warns that 80 percent of carbon emissions infrastructure has already been built and is in operation. We cannot afford to add any new carbon intensive infrastructure that will continue to pollute for 30-50 years. They too warned in their 2011 World Energy Outlook report that we are on a 4-6 degree Celsius trajectory. A recent Price WaterhouseCoopers report warned that Business as usual Carbon emissions heading towards 6°C (10.8°F) of global warming this century. So there is widespread agreement from science and scientists, energy experts and experts in global economics and accounting that we are facing a climate meltdown.

Related: 4 Degrees or More? Climate Change: The Critical Decade - a speech by Professor Hans Joachim SchellnhuberDirector of PIK. Speech delivered at a Climate Science conference in Melbourne, Australia, July 2011.

20 years of talk, little action

Yes, the world has spent 20 years talking about climate change - since the 1992 Rio De Janeiro conference - but with only minor action around the edges to change our actual carbon intensive habits.

Scientists made projections for possible impacts for 2 degrees warming, but when considering 4 degrees or 6 degrees (7.2 or 10.8°F) it becomes so much more difficult with tipping points and feedback mechanisms, and the whole climate system moving beyond anything we have experienced, and a rate of change that is also well outside past geologic rates of paleo-climatic change. If we reach and surpass 4 degrees of warming it will be disastrous on so many levels. Keep in mind that 4 degrees of global warming (sea and land) equates to average land temperature increases of 6 to 10°C (7.2 or 10.8°F) for many areas. So that last heatwave you endured, imagine what it would be like with an additional 6 to 10°C (7.2 or 10.8°F) Celsius on top. Because by the end of the century that will be the new heatwave normal.

The 2 degree limit was decided upon several years ago by policy makers based upon scientific advise, of a level of warming to keep within for a 50 percent chance of maintaining civilization within a relatively reasonable climate system, and to avoid the large destructive impacts which are likely to come with exceeding this level. The 2 degree limit was agreed to at UN climate talks in Copenhagen in 2009, and reaffirmed in Cancun in 2010 and Durban in 2011. But over the years the science of climate change has continued to refine its data and analysis. There are now climate scientists arguing that perhaps the safe level is 1 degree (1.8°F) of Global Warming, or at most 1.5°C (2.7°F). This is the level that the 350.org movement has also adopted.

We are presently at 0.8°C (1.44°F) of warming, with perhaps another0.8°C (1.44°F) degrees already in the pipeline due to the strong inertia in the earth's climate system. The oceans warming have built up an enormous amount of heat that will power increasing temperatures even if we stopped all carbon emissions today.

Attribution of Extreme weather events to Climate Change

Our experience with extreme weather disasters shows a growing trend, according to the large re-insurance companies statistics. We know that climate change is systematically a part of all extreme weather events now like Hurricane Sandy. While scientists used to say any one extreme weather event could not be attributed to climate change, that is no longer the case. Scientists now run probabilistic modelling of extreme events and can attribute that climate change is likely to have played a significant part in some single extreme weather events.

While our changing climate may not initiate weather events, changed climate conditions can exacerbate and greatly intensify those events increasing the likelihood of death and destruction.

Climate scientists have estimated an 80 percent chance that climate change was responsible for the July 2010 Russian heatwave. Similarly, the European heatwave of 2003 (PDF), and the floods in England and Wales in 2000 (Abstract) have all been assessed as being caused at least in part by anthropogenic climate change through statistical modelling of probabilities and fractional attributable risk studies.

The Intergovernmental Panel on Climate Change (IPCC) released the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX) in November 2011 with details of extreme weather event trends and assessment.

Poorest hit hardest

Extreme weather and Climate change will affect everyone, rich and poor, but disproportionately the poor will be hit hardest. This will occur in Western developed nations like the US experience of hurricane Sandy where those with money and means will easily adapt while the poor have to rely on mutual aid and welfare and back breaking work to adapt to the disaster. Developing countries in the Caribbean, Africa and Asia will have little money for recovering from climate disasters and future adaptation. Before striking the US East coast, Hurricane Sandy devastated crops and infrastructure in the Caribbean, highlighting food security and the inadequacy of basic health infrastructure to cope with this disaster.

"At the very moment that Africa is poised to make its mark on the global economy, this report shows us that the continent will be one of the worst affected by climate change. We need strong commitments and urgent action to mitigate the impact, and to assist countries to survive and develop in a context of climate change and extreme weather patterns." said Tina Joemat-Pettersson, Minister of Agriculture, Forestry and Fisheries of the Republic of South Africa.

Ali Bongo Ondimba, President of the Gabonese Republic said "A 4 degree world would be devastating for developing countries and the poor would be hit hardest. Gabon is committed to building climate smart development."

"A 4 degree warmer world can, and must be, avoided - we need to hold warming below 2 degrees," said World Bank Group President Jim Yong Kim. "Lack of action on climate change threatens to make the world our children inherit a completely different world than we are living in today. Climate change is one of the single biggest challenges facing development, and we need to assume the moral responsibility to take action on behalf of future generations, especially the poorest."

"The world must tackle the problem of climate change more aggressively," Kim said. "Greater adaptation and mitigation efforts are essential and solutions exist. We need a global response equal to the scale of the climate problem, a response that puts us on a new path of climate smart development and shared prosperity. But time is very short."

Reaction from Small Island States

Small island states are being impacted now and have strongly argued a 2 degree limit is far to much and threatens their survival as nations and cultures of the world. They prefer that we do not exceed a maximum limit of 1.5 degrees of warming. Tuilaepa Sailele Lupesoloai Malielegaoi, the Prime Minister of Samoa commented: "This new World Bank Report is very alarming, not just for Samoa and the Pacific region, but for the whole world. It validates compellingly the scientific presentation made to SIDS leaders during their recent Summit on the margins of the United Nations General Assembly. The impacts of climate change are already being felt, and that is why SIDS are calling for a cap of 1.5 degrees Celsius. Going beyond 2 degrees towards a 4 degree world would be cataclysmic. The dire consequences now predicted in the World Bank report will unavoidably be given greater focus in the 3rd international conference on SIDS that Samoa will host in 2014. I have always maintained that climate change knows no boundaries and as a global problem we must all work together and act now."

"For small island developing states, a four degree world is unthinkable. Already at 0.8 degrees above pre-industrial levels, islands and the rest of the world are experiencing devastating impacts of climate change; some seven years ago, Hurricane Ivan caused damages worth 200% of Grenada's GDP and to rebuild from the hurricane dramatically increased the island's financial indebtedness. There is a growing consensus that the deadly and costly Hurricane Sandy is climate related. Islands like Grenada have been calling on the international community to limit warming to well below 2.0 degrees Celsius, and believe that below 1.5 degrees is preferable. Averting climate disasters must be a top priority for the international community. We therefore commend the World Bank on this report." said Tillman J. Thomas, Prime Minister of Grenada, co-Chair of the Global Islands Alliance and former chair of the Alliance of Small Islands States

Climate Impacts: Heat Waves, sea level rise, more intense extreme weather

The report details 4°C scenarios : the inundation of coastal cities; increasing risks for food production potentially leading to higher under-nutrition and malnutrition rates; many dry regions becoming dryer, wet regions wetter; unprecedented heat waves in many regions, especially in the tropics; substantially exacerbated water scarcity in many regions; increased intensity of tropical cyclones; and irreversible loss of biodiversity, including coral reef systems.

"The Earth system's responses to climate change appear to be non-linear," points out PIK Director, John Schellnhuber. "If we venture far beyond the 2 degrees guardrail, towards the 4 degrees line, the risk of crossing tipping points rises sharply. The only way to avoid this is to break the business-as-usual pattern of production and consumption."

The report - Turn Down The Heat: Why a 4°C Warmer World Must be Avoided - summarizes a range of the direct and indirect climatic consequences under the current global path for greenhouse gas emissions. It is an up to date snapshot in time of current scientific findings on the existing and projected impacts of climate change. Key findings include:

Extreme heat waves, that without global warming would be expected to occur once in several hundred years, will be experienced during almost all summer months in many regions. The effects would not be evenly distributed. The largest warming would be expected to occur over land and range from 4° C to 10°C (7.2 to 18°F). Increases of 6°C (10.8°F) or more in average monthly summer temperatures would be expected in the Mediterranean, North Africa, Middle East and parts of the United States.

Sea level-rise by 0.5 to 1 meter by 2100 is likely, with higher levels also possible. Some of the most highly vulnerable cities are located in Mozambique, Madagascar, Mexico, Venezuela, India, Bangladesh, Indonesia, the Philippines and Vietnam.

The most vulnerable regions are in the tropics, sub-tropics and towards the poles, where multiple impacts are likely to come together.

Agriculture, water resources, human health, biodiversity and ecosystem services are likely to be severely impacted. This could lead to large-scale displacement of populations and consequences for human security and economic and trade systems.

Many small islands may not be able to sustain their populations.

Biodiversity would suffer in a 4 degree warmer world. The report says

Significant effects of climate change are already expected for warming well below 4°C. In a scenario of 2.5°C warming, severe ecosystem change, based on absolute and relative changes in carbon and water fluxes and stores, cannot be ruled out on any continent (Heyder, Schaphoff, Gerten, & Lucht, 2011). If warming is limited to less than 2°C, with constant or slightly declining precipitation, small biome shifts are projected, and then only in temperate and tropical regions. Considerable change is projected for cold and tropical climates already at 3°C of warming. At greater than 4°C of warming, biomes in temperate zones will also be substantially affected. These changes would impact not only the human and animal communities that directly rely on the ecosystems, but would also exact a cost (economic and otherwise) on society as a whole, ranging from extensive loss of biodiversity and diminished land cover, through to loss of ecosystems services such as fisheries and forestry (de Groot et al., 2012; Farley et al., 2012).

Climate change will also facilitate the spread of invasive species and pests and can "catalyze rapid shifts in ecosystems such as sudden forest loss or regional loss of agricultural productivity resulting from desertification". Higher temperatures will also make for more intense extreme fire-weather which will drive biome shifts.

Non-linear and cascading impacts

There are also risks of nonlinear or cascading impacts that are much harder to quantify, but need to be assessed as their impact would be substantial. These are likely to be triggered when we cross critical thresholds. Crossing these tipping points will produce large-scale and disruptive irreversible changes in the climate system. Such tipping points include as examples: Amazon Rainforest Dieback, collapse of ocean ecosystems due to warming and acidification, collapse of West Antarctic and Greenland ice sheets, but there are several more including destabilisation of the Monsoons.

The tipping point for Amazon dieback is estimated to be near 3-5°C global warming (Lenton et al. 2008; Malhi et al. 2009; Salazar and Nobre 2010). "A collapse would have devastating consequences for biodiversity, the livelihoods of indigenous people, Amazon basin hydrology and water security, nutrient cycling, and other ecosystem services."

Ocean ecosystems. Coral reefs will struggle to survive at 1.5 degrees and are projected to experience widespread coral reef mortality at 3-4°C above pre-industrial. This will impact hundreds of millions of people economically dependent on reef ecosystems, not to mention the storm surge protection they provide.

West Antarctic Ice sheet locks up 3 metres of sea level rise, and from research we know it is losing mass and is inherently unstable, but we don't even have a threshold estimate.

Greenland Ice Sheet locks up 6-7m of sea level rise and is losing mass. Recent research has estimated a tipping point may be as low as 1.5°C

When only one sector is impacted, compensations can often be made, but when several sectors feel the brunt of global warming, the interactions between the sectors can compound the impact. "If changes were to be small, it is plausible that there would be few interactions between sectors. For example, a small change in agricultural production might be able to be compensated for elsewhere in another region or system. However, as the scale and number of impacts grow with increasing global mean temperature, interactions between them seem increasingly likely, compounding the overall impact."

So can we adapt to a 4 degree or 6 degree world?

Some people will likely survive, but such a level of global warming will pose severe difficulties for industrial society adapting. Heatwaves will buckle our railway lines causing transport chaos. Increasing intensity of cyclones and storm surges will swamp our coasts and coastal infrastructure. Extreme weather, high temperatures, changes in precipitation will reduce our crop yields and raise food security alarms. As transport and freight is disrupted, our social fabric will start to tear apart at the seams.

The Executive summary of the report concludes:

Thus, given that uncertainty remains about the full nature and scale of impacts, there is also no certainty that adaptation to a 4°C world is possible. A 4°C world is likely to be one in which communities, cities and countries would experience severe disruptions, damage, and dislocation, with many of these risks spread unequally. It is likely that the poor will suffer most and the global community could become more fractured, and unequal than today. The projected 4°C warming simply must not be allowed to occur--the heat must be turned down. Only early, cooperative, international actions can make that happen.

The report puts forward that a 4°C world is not inevitable and that with sustained policy action warming can still be held below 2°C.

But some climate scientists like Kevin Anderson think we are past being able to achieve a global warming limit of 2 degrees of warming. (Climate Change: Going Beyond Dangerous, November 2011) There are simply too many socio-political hurdles to decarbonising western economies and the global economy to achieve this target.

Limiting warming to 2 degrees would take a herculean effort by Government and business leaders as envisaged in Paul Gilding and Norwegian Professor of Climate Dynamics Jorgen Randers 2009 paper: the One Degree War Plan. Paul Gilding at a talk at TED in March 2012 talked a little of the great disruption he sees coming and advocates choosing life over fear and working on solutions.

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