Two or Three Degrees - What Could Happen?

Did you know that in the last million years the global temperature has not been more than 1 degree Centigrade hotter than it is now? In an earlier blog I listed some of the things that could happen if the global temperature reached one degree higher, but as my previous post noted, it seems guaranteed to get at least a degree or two hotter than that. What will this mean, what changes can we expect?

Here is a list of predictions if global temperatures go 1 - 2 degrees above 2008 global temperatures, or about 1.7 - 2.7 degrees C above preindustrial levels. These come from the book and DVD “Six Degrees”, by Mark Lynas and National Geographic, respectively. These are all predictions made by scientists, either based on what we know of the past (paleoclimatology) or on models of the future. Things could turn out better or worse than these predictions indicate, but this is the best and most complete list that I’m aware of.

-We will be on the brink of runaway global warming – many think this will be the tipping point, when feedback could take over.
-The tundra in the North will almost totally disappear, and the permafrost boundary will move hundreds of miles north.
-We will lose the vast majority of coral reefs and the millions of species that depend on them.
-The oceans will be too acidic for the formation of shells, imperiling shellfish, plankton, and most other life in the oceans (since the food chain depends on plankton).
-Over a third of all species will be committed to extinction by 2050, and well over a million species will already be extinct by then.
-Coastal cities around the world will experience more floods.
-By 2040 the average summer will be hotter than 2003, when a heat wave killed thousands of people in Europe.
-There will be catastrophic wildfires and water shortages in Europe and the Mediterranean area.
-In China, shifting monsoons will bring widespread drought, food shortages.
-India will see decreases in wheat and rice production and large scale die-offs of forests.
-Poorer countries, especially Africa, will have food shortages. Most of S. America will have corn shortages. World food prices will soar during lean years.
-Some Peruvian glaciers will shrink 40-60% by 2050, while others (including one that supplies Lima’s water) will be completely gone.
-Widespread conflicts seem likely.
-Water supplies in California may decline by a third to three quarters, while water supplies for Oregon and Washington may decline 20 to 70%.
-Flooding, and fires will increase in many parts of the world
-Sea level could rise 5 meters (16.4 feet) by 2100 even if it gets no hotter than this.
-Greenland may have no ice by around 2150, forcing half of humanity to move to higher ground.
-Two feedbacks: The earth’s largest carbon sink, the oceans, will begin absorbing much less of the excess CO2, and phytoplankton will no longer remove billions of tons of CO2 from circulation per year.


And here is what scientists predict for 2 - 3 degrees above current temperature, or 2.7 - 3.7 degrees above preindustrial levels. You have to go back 3 million years to find a time when the world was this hot. The world could get this hot as early as 2050 if we do nothing to stop it.

-The last time the world was this hot, beech trees grew in Antarctica, and Northern Greenland had pines and other conifers. El Nino patterns occurred every year. Sea level was 25 meters (49 feet) higher than now. And yet CO2 levels were only 360 to 400 ppm (we are currently around 386 ppm).
-El Nino could again happen every year. This will cause extreme drought in Indonesia and Australia and more rain for the South American West Coast. The 1912 El Nino caused storms in the North Atlantic, floods in China, drought in the Amazon, crop failures in Australia, famine in North Africa and India (no monsoon). The effect could be even stronger than 1912.
-Australia will be much hotter than now, with more fires and drought and agricultural collapse in the south.
-Snow caps in the Alps will all but disappear.
-Heat waves like those in the summer of 2003 will become the norm for Europe.
-More droughts and fires in parts of every continent.
-The Mediterranean will begin to turn into a desert as the Sahara jumps the sea.
-Monsoons will become more variable, flooding more some years, not raining enough other years, both affecting crops.
-Parts of Africa will get more rains and floods, other parts less water and more droughts. Malaria and dengue fever will move to higher altitudes and latitudes.
-The Indus, which waters the fields of Pakistan, will be dry for months of the year. Other rivers fed by Himalayan glaciers and supplying water to China, India, and other countries will begin to dry out.
-Hurricanes will probably be stronger, with Category 6 storms occurring.
-New Orleans may already be abandoned.
-New York City will face flooding: 100 year floods will happen roughly every 20 years by the 2050s and every 4 years by the 2080s.
-In England, 150 year floods could happen every 7 to 8 years by the 2080s.
-On the East coast, ocean levels could rise a meter, and coastal erosion could average 3 meters per year.
-There will be perennial drought and famine in much of southern Africa. Botswana will be entirely covered by shifting sand dunes by 2070, and no longer able to support human life.
-Yields of rice, wheat, and corn will decline in temperate regions and see crippling declines in tropical regions. More crops will grow closer to the poles, but the IPCC estimates there will be a net deficit with a 2.5 degree further rise.
-The Arctic will have an 80 to 100 percent reduction in sea ice.
-Many scientists predict a 3 degree rise will push us over the tipping point, if 2 degrees hasn’t already done so.
-A feedback loop will turn the Amazon into an arid savannah as early as 2027, which could raise temperatures one degree more, meaning 3 - 4 degrees hotter than now.
-Still another feedback is that vegetation and soils could release CO2 instead of absorbing it, adding an additional 90 - 250 ppm by 2100, which would cause the temperature to rise another 0.6 to 1.5 degrees C.
-Taking the previous two feedbacks together, 3 degrees could lead to 4.5 - 5.5 degrees higher than now, or 5.3 – 6.3 degrees C above preindustrial levels.
-The planet’s basic life support systems may begin to break down.
-Corals will bleach annually and will be nearly gone.
-The climate of 40 to 85% of the earth will shift towards the poles, too quickly for many species to migrate.
-The climate of 10 to 50% of the earth will be gone completely, no longer existing anywhere on earth.
-A third to a half of all species in existence today will be extinct by 2050.

So does this mean we are doomed? I think if the feedbacks occurred, billions of people would probably suffer and die, but I don't know if the human species will die off completely. That depends partly on what we do and partly on how the various feedbacks play out.