Storms drive powerful swells; so for an increase in storm power the waves will actually in turn become increased in size. Though storms are supposed to create larger swells and better surf, waves are actually decreasing in size globally. Rising sea levels decrease the potency of storms; hurricanes and winds have a smaller impact on surf breaks only when the tides are higher. Globally, with an increase in storm frequency and power, swells will become stronger and happen more often. The quality of surf is not yet known to the future swells due to variables such as sea level, ocean currents, and location on the earth. Additionally, the force driving the swells may vary due to the condition of global ocean currents. Since Earth's oceans are affected by global warming, thermal stress affects the coral reefs, slowly withering away until the coral bleaches. Coral bleaching eventually kills the coral. Sea level rise expands the ocean's area, acquiring more sediment as it grows. With more sediment under the sea, coral begins to become buried alive. As sedimentation occurs, reef breaks turn into beach breaks; which can have positive or negative impacts; depending on the circumstances of the break (wind, depth, location). Anthropogenic waste running off into the sewage lines that feed to the ocean, sprouting harmful algae blooms and murky water that limit the amount of sunlight coral reefs can absorb. Coral reefs provide some of the world's best waves; though they may not be around for long. Coral reefs have a narrow window of temperature in which they can live. With an average increase in global temperatures of one degree per decade, and 90% of the heat being absorbed by the ocean. Coral reefs are in danger of becoming extinct by 2030. Coral reef loss creates beach breaks; which alter the nature of the wave. With an increase of carbon emissions from the combustion of fossil fuels, the ocean acts as a sink for all of the extra CO2 in the atmosphere. CO2 naturally increases the acidity of the ocean, throwing the pH of the ocean to a more acidic state. Currently the acidity of the ocean has increased by 30%. The increase has led to coral reefs degrading, therefore impacting all of the reef breaks. Carbon dioxide absorbed into the ocean from the atmosphere reduces calcification rates in reef-building and reef-associated organisms by altering seawater chemistry through decreases in pH. In 2008, surfers and environmentalists opposed a toll road project in Orange County, California that would have changed sediment patterns and affected the world-class "Trestles" surf break north of San Onofre State Beach which attracted 400,000 surfers in 2007.