A much-awaited United Nations report on the science behind climate change says scientists are 95 percent  sure that humans are the “dominant cause” of global warming since the 1950s. The document, which is meant to serve as a guideline for policymakers to shift towards greener energies, warns that the impact of greenhouse gas emissions could linger for centuries.

The report by the Intergovernmental Panel on Climate Change (IPCC) is considered the most comprehensive document on our understanding of the mechanics of a warming planet and the physical evidence behind it.

The following are the main findings of the report:

• Global warming is “unequivocal,” on the ground, in the air and in the oceans. And It’s “extremely likely”  or 95 percent likely that human activities, led by the burning of fossil fuels, are the main cause of a rise in temperatures since the 1950s.
• Concentrations of carbon dioxide and other greenhouse gases in the atmosphere have increased to levels that are unprecedented in at least 800,000 years. The burning of fossil fuels is the main reason behind a 40 percent increase in C02 concentrations since the industrial revolution.
• Short, individual periods, such as 1998, which was an unusually warm year, are influenced by natural variability and are not an indicator of long-term climate trends.
• Global temperatures are likely to rise by 0.3 to 4.8 degrees Celsius, or 0.5-8.6 Fahrenheit, by the end of the century depending on how much governments control carbon emissions.
• Sea levels are expected to rise a further 10-32 inches (26-82 centimeters) by the end of the century. That will pose a threat to coastal cities from Shanghai to San Francisco.
• The Greenland and Antarctic ice sheets have been shrinking over the past two decades. Glaciers have continued to melt almost all over the world. Arctic sea ice has shrunk and spring snow cover has continued to decrease, and it is “very likely” that this will continue.

At the end of the year you get flooded with reviews of 2012. We won’t bore you with another one. Well, we can’t do without revisiting last year at all. So here are some interesting bits and pieces of info on what happened in 2012  from a climate change perspective.

Oil and coal are set to be phased out sooner or later, scientists are busy exploring alternatives. One of them comes straight from the gut. No kidding. In January they presented genetically engineered gut bacteria that could convert seaweed into ethanol. If the process is feasible on large scales, this may help solve the fuel-versus-food- dilemma.

Flood protection for coastal areas, habitat to thousands of species: coral reefs maintain several critical roles in the Earth’s ecosystems – some of which are under particular threat due to climate change. But at the same time corals themselves are threatened by global warming, as NASA scientists confirmed in February  following one of the most comprehensive studies yet undertaken on the issue. Rising water temperatures and increasing acidification lead corals to dissolve and die – and the loss of their protective role.

But there is also good news: There is a shift in the climate change debate – from “does climate change exists?” we’ve moved on to “what impacts does climate change have?” and in the best case “how can we prevent it?”. March saw the public discuss a question – well in line with this new level of awareness: Has climate change been underestimated so far? Scientists warned, the global mean temperature could rise by 3 degrees Celsius by 2050.

Climate change is not an isolated problem, but associated with other issues – like food security for example. So, in April, experts and locals discussed at the Climate Smart Agriculture in Asia workshop how to secure rice production in a warming world with more intense droughts and rainfalls. Rice is the staple diet for more than half of the world’s population. At present some 870 million people are already suffering from hunger – not to imagine how this situation will worsen if rice production falls short.

In May world leaders met  in Bonn for climate conference – but were not able to agree on any effective measures.

At least a little more optimism could be found at the Rio+20 conference in June: Our reporters Kerstin and Philipp were there for you, presenting innovative people, their ideas and opinions. Re-experience their trip here.

To mitigate global warming, researchers also come up with controversial ideas – most of them attempts to fix the climate by resorting to geoengineering. One idea was highly disputed in July: by dumping iron into the ocean, the ocean’s ability to act as a carbon sink should be increased.

Even some climate skeptics were finally convinced of the reality of climate change, when severe droughts and heat waves hit the United States in the summer months around August. Russia also suffered from extreme droughts, but for the US 2012 has been the hottest year ever recorded.

From dry and hot regions to cold ones: in the middle of September the Arctic ice cover reached an all-time low. Ice melting during the summer is not unusual, but the rate of melting and the large area affected astonished researchers.

Watching  the densely populated US East coast brace for the impact  of super hurricane Sandy in October, many people around the world paused – the effect of climate change appeared so undeniable as hardly ever before:  More and more people in the United States – the developed country with the highest CO2 emissions per capita – start believing that climate change is real.

Following the strong winds, in November researchers declared that sealevels are rising quicker than expected: in fact, the oceans are rising 60 percent faster than previously thought.

In December super-thyphoon Bopha hit the Phillipines, being far stronger than the storm that killed more than 1,200 people in the same region a year earlier. Furthermore the next IPCC report – to be published in 2013 or 2014 – was leaked, revealing that CO2 emissions caused by humans are now “virtually certain” to be the reason for global warming. As this is not really new to a lot of people, country leaders discussed at the climate conference in Doha, Qatar how to deal with climate change. Our reporters Kerstin and Klaus went to Doha for you – revealing all the green ideas they encountered there.

What would you say – anything else we should include to complete our 2012’s climate-change-review?

At the Doha climate change conference, delegates of the COP18 again try to find a practical way how to (further) reduce greenhouse gas emissions. The importance of this goal was again highlighted by a new study released recently by the Potsdam Institute of Climate Impact Research (PIK): Researchers found out that sealevel rose much quicker than projected by the latest IPCC report.

That’s what they saw when comparing the model calculation with real satellite data from 1990 to 2011.  According to those satellite measurements, oceans are rising 60 percent faster than previously thought. In absolute numbers: the IPCC report from 2007 projected additional 2 mm sealevel per year, satellite data revealt a rate of 3.2 mm per year.

Which might seem less in numbers, can make a huge difference in reality. Already for the projected 2 mm, researchers warned this might lead to flood waters, more extreme storms, and salted ground water. Yet, nobody can forecast what exactly is to happen with a higher rate of sealevel rise. But nonetheless, threat for coastlines and megacities continues to increase. Especially if no reliable mechanism will be found to reduce CO2 emissions – as in consequence sealevels will rise by several meters at the end of this century.

The UN’s Intergovernmental Panel on Climate Change (IPCC) came out with a report recently that said renewable energy could make up 77% of the entire world’s energy needs by the year 2050. Yes, 77%! If that happened, we would slash one-third of the world’s greenhouse gas emissions and hold global temperatures under 2 degrees celsius.

The study included a series of renewable energy forms that could contribute to a very green future: solar, hydropower, wind, geothermal, and bioenergy. So what’s the catch? Well, of course, it all depends on politics and policy. According to the study, each country has to fight political obstacles and complications to make sure environmentalism is a top priority.

What are the obstacles and complications in your country that are preventing good climate policy?