The rhetoric has been high ahead of the Rio+20 conference starting in the Brazilian city today. It is a gathering that marks the 20th anniversary of the original Rio de Janeiro Earth Summit, at which landmark treaties to curb climate change and arrest the extinction of species were agreed. It is also the biggest event ever organised by the UN, and one that its Secretary General, Ban Ki-moon, says is "too important to fail".
For all the warm words, however, expectations of real progress are low. Not only are some prominent world leaders – Barack Obama, for example – not attending. The precedents are also far from promising: in the two decades since the world signed up to a blueprint to save the planet, just four of 90 top green goals have seen significant advances.
Although there have been breakthroughs in atmospheric ozone levels, the removal of lead from petrol, and the provision of clean drinking water in the world's urban areas – with lesser improvements in sanitation in rural areas – little has changed with regards to oceanic pollution, groundwater quality, or climate change. Indeed, there have been deteriorations in the amounts of water available, and in both fish stocks and coral. The world's rainforests also continue to be destroyed, removing a major natural carbon store, and wiping out species at an unprecedented rate. Most critical of all, attempts to curb greenhouse gas emissions are failing. Levels of CO2 have now exceeded 400 parts-per-million – just 50ppm lower than the level that scientists fear will trigger irreversible, and catastrophic, climate change.
With so little progress made over decades when the global economy was booming, is there much cause for hope now that times are hard? Perhaps. The key issue will be how poorer nations can fuel economic growth without raising their carbon emissions. The problem is that developing countries want the rich world to subsidise clean energy projects, but financially exhausted Western nations are unwilling to pay.
Of the many strands of negotiations ahead of the Rio+20 summit, however, none succeeded in reaching an agreement. Canada does not want to declare safe drinking water a human right. The Vatican is trying to veto family planning, again. Many countries object to the commitment to phase out subsidies on damaging fossil fuels. And the Chinese-led G77 bloc of 131 developing countries has put a red line through much of the proposed summit text.
Meanwhile, other commitments have been diluted by a lack of costing or timetable. The text confirms, for example, that rich and poor countries have "common but differentiated responsibilities" in moving towards sustainable development; but it does not endorse the $30bn-plus a year that developing countries want in exchange for creating low-carbon economies. Indeed, the fact that the draft text uses the word "encourage" some 50 times, but "must" only three, speaks volumes about the force of its contents.
With world leaders at the G20 in Mexico, the euro crisis rumbling ominously, and even developing economies starting to dip, the timing is bad for a conference on sustainable development. But progress is not impossible. There is still a realistic chance that economic growth will be redefined to include environmental quality, biodiversity and social stability. And there may yet be a commitment to a new set of Sustainable Development Goals, proposed by Guatemala and Colombia, to give specific yardsticks to measure green global progress.
Such ambitions might sound sadly limited, after the soaring pre-summit hyperbole. But they are, at least, realistic. And they would still be genuine, if small, steps forward – even if what is needed is bigger, far more rapid strides.