It’s too late to limit the world to 2°C of global warming, the level identified by climate negotiators as the threshold beyond which the world faces “dangerous” levels of climate change, said former NASA scientist and UK Environment advisor Sir Bob Watson today in a lecture at the American Geophysical Union. That’s because, by his interpretation of the best estimates of current climate models, rich countries would have had to halt the growth in their greenhouse gas emissions back in 2010.

Of course, the 2°C threshold was always somewhat arbitrary, the product of a consensus that was as much political as scientific. (Unfortunately, some assessments of its validity as a policy tool suggested that it was in fact too generous a limit.)

Despite our tardiness, Watson said that little has changed about what we must do to avert even worse climate change, reported Mark Fischetti of Scientific American. We’ll need plenty of carbon-free electricity, including nuclear power and fossil-fueled plants paired with carbon capture and storage systems, not to mention a high price on carbon in order to curb its use in all sectors and industries.

Scientists have also proposed “geoengineering,” or the process of deliberately manipulating Earth’s climate by affecting how much sunlight our atmosphere reflects back into space. One proposed method would essentially create an artificial volcano to cool the earth. Watson argued that such schemes will mostly be a distraction from the reductions in carbon emissions that we have to accomplish one way or another.

“And to be honest, we screwed up the earth by not understanding it, so I’m not sure trying to engineer it is a good idea,” said Watson.

A new report from the World Bank presented at the Doha climate change conference says that, like much of the developing world, the Middle East is already being squeezed by two climate-driven trends: increasing urbanization and increasing vulnerability of urban areas.

In the report, experts at the World Bank recognize that urbanization is taking place for a number of reasons, including displacement from war and high fertility rates. But they also cite examples of populations moving to cities specifically because of a changing climate. For example, the UN estimates that in Syria, a four-year drought drove almost 800,000 rural Bedouin villagers to camps around the cities of Aleppo, Damascus, and Homs.

At the same time, the cities to which people are moving are increasingly vulnerable. In the Middle East, in particular, cities are concentrated along rivers and coastal areas that are subject to rising sea levels, flooding and extreme weather.

According to one report published in 2009 (PDF), 1 meter of sea level rise (the conservative estimate for where we’ll be by the end of the century) would inundate 41,500 square kilometers (16,000 square miles) of coastal area in the Middle East, directly impacting 37 million people.

Temperatures are rising in the Middle East, and in general, the area is drying out. Yet delivering enough water for drinking and sanitation is already an issue in the region’s megacities, says the World Bank report:

In coastal cities in Lebanon, for example—particularly in the capital Beirut where half the population lives—water shortages are frequent because local supplies are incapable of meeting rising demand. Lacking access to adequate water services, people often illegally tap shallow aquifers, resulting in serious seawater intrusion. In an attempt to reduce pressure on heavily populated Cairo, the government has encouraged urban development in desert ar- eas, which has presented serious challenges in procuring water supplies over large distances. In Jordan, the population is increasingly concentrated in the highlands, several hundred meters above most prospective water resources.

Finally, there’s the issue of ever greater dependence on imported food as adaptation measures, rising temperatures, and scarce water drive more people out of agriculture. In 2008, Egypt saw riots over scarce bread, leading then-dictator Hosni Mubarak to order the army to bake more of it. Arab countries in the Middle East and North Africa represent 5% of the world’s population but already consume more than 20% of the world’s grain exports. Those imports are rising rapidly.

So how will countries in Middle East provide for an ever more urban, vulnerable and import-dependent population? The report suggests that families will have to diversify their sources of income. But also, in many cases, they will simply be split apart as men move to cities for work while women try to hold on to rural homesteads.