**3.2.4 Extreme weather, tropical cyclone, and list of atlantic hurricane records**

Since the late 20th century, changes have been observed in the trends of some extreme weather and climate events, e.g., heat waves. Human activities have, with varying degrees of confidence, contributed to some of these observed trends. Projections for the 21st century

Global Trends of Fossil Fuel Reserves and Climate Change in the 21st Century 181

The oceans serve as a sink for carbon dioxide, taking up much that would otherwise remain in the atmosphere, but increased levels of CO2 have led to ocean acidification. Furthermore, as the temperature of the oceans increases, their absorptivity for excess CO2 decreases. The oceans have also acted as a sink in absorbing extra heat from the atmosphere. This extra heat has been added to the climate system due to the build-up of GHGs. More than 90 percent of

Global warming is projected to have a number of effects on the oceans. Ongoing effects include rising sea levels due to thermal expansion and melting of glaciers and ice sheets, and warming of the ocean surface, leading to increased temperature stratification. Other

a. *Number of tropical storms and hurricanes per season*: This bar chart shows the number of

 Smallest tropical cyclone on record: Marco - 2008 - gale force winds extended 10 mi (20 km) from storm center (previous record: Cyclone Tracy 1974 - 30 mi (50 km)) b. *Ocean Acidification*: About one-third of the carbon dioxide emitted by human activity has already been taken up by the oceans. As carbon dioxide dissolves in sea water, carbonic acid is formed, which has the effect of acidifying the ocean, measured as a change in pH. The uptake of human carbon emissions since the year 1750 has led to an average decrease in pH of 0.1 units (*IPCC 2007d. "3.3.4 Ocean acidification*). Projections using the SRES emissions scenarios suggest a further reduction in average global

The effects of ocean acidification on the marine biosphere have yet to be documented. Laboratory experiments suggest beneficial effects for a few species, with potentially highly detrimental effects for a substantial number of species. With medium confidence, Fischlin *et al.* (2007) projected that future ocean acidification and climate change would impair a wide range of plank tonic and shallow benthic marine organisms that use aragonite to make their shells or skeletons, such as corals and marine snails (pteropods),

c. *Oxygen Depletion*: The amount of oxygen dissolved in the oceans may decline, with

d. *Sea level rise*: Sea level has been rising 0.2 cm/yr, based on measurements of sea level rise from 23 long tide gauge records in geologically stable environments. Sea level was

adverse consequences for ocean life (*Crowley TJ, 1988; Shaffer G, et al., 2009*).

warming that occurred over 1960–2009 is estimated to have gone into the oceans.

Costliest tropical cyclone: Hurricane Katrina - 2005 - \$81.2 billion in damages.

surface ocean pH of between 0.14 and 0.35 units over the 21st century.

possible effects include large-scale changes in ocean circulation.

named storms and hurricanes per year from 1893-2010.

Fig. 10. Worldwide cyclone records set by Atlantic storms

with significant impacts particularly in the Southern Ocean.

**3.2.6 Role of the oceans in global warming** 

suggest continuing changes in trends for some extreme events. Solomon *et al.* (2007), for example, projected the following likely (greater than 66% probability, based on expert judgment) changes:


Projected changes in extreme events will have predominantly adverse impacts on ecosystems and human society.
