Two satellites Jason 1 in 2001 and Jason 2 in 2008 were launched from Delta II rockets from Vandenberg Air Force Base. They have been measuring sea level height over most of Earth using an extremely precise radar altimeter. It transmits radio waves from the satellite to the oceans surface and measures the time it takes for the radio waves to bounce back.
This technique has proved to be extremely precise and accurate.
These satellites give us a global view of our changing oceans with such exquisite accuracy that even the yearly rise and fall of global sea level is visible, caused by the transfer of water to and from the continents in the form of rain and river runoff, said climate scientist Josh Willis of NASAs Jet Propulsion Laboratory in Pasadena. Willis has been an authority on sea-level changes for many years.
Sea-level change is probably the best way to measure climate change. The oceans cover 70 percent of Earths surface, receive 80 percent of the rainfall and hold 97 percent of Earths water. The other 3 percent is held in land, ice, ground water, and freshwater lakes and rivers. Only a small percentage of the total water (0.001 percent) is in the atmosphere. However, this 0.001 percent can have profound effects on all our lives.
The ocean has a thousand times more heat capacity than the atmosphere. When water warms, it expands. During strong El Niño events, when seawater temperatures along our coastline are warmer than normal, water levels can actually be several inches higher than those predicted in the tide tables. This is due to the thermal expansion of the upper levels of the ocean. This, along with melting glaciers and ice sheets in both hemispheres, pushes sea levels higher over the long term. This makes sea-level change a vital indicator of climate change.
The average rise in the sea level has been fairly steady over the past few decades at about 3.1 millimeters per year. From late 2010 into early 2011, global sea level fell by about half a centimeter. Since that anomaly, the relentless rise in sea level has resumed.
So what caused sea levels to stop rising briefly in 2010 and 2011? Willis says you can blame it on the cycle of El Niño and La Niña in the Pacific.
Out over the ocean, the suns light combined with Earths winds to evaporate enormous amounts of seawater into nearly pure water vapor in the atmosphere. While most of it falls right back into the ocean as rain and snow, some of it falls over land.
A strong La Niña pattern developed last year. This sudden shift in the Pacific changed precipitation patterns all across the globe, bringing unimaginable floods to places such as Australia, which ended one of the worst droughts in history. Many locations east of the Rocky Mountains last year also experienced record floods. The Mississippi River reached levels not seen by anyone alive today. Severe floods also raged across the Amazon basin, the largest watershed in the world. By late 2011, all that rain finally made its way back into the oceans, bringing the sea level back up again.
Historical records indicate gradual changes in sea level over hundreds or thousands of years, but since the end of the last ice age, we have not seen anything quite as dramatic as the past few decades of rising sea levels. This leads me to believe that we are contributing to climate change with our emissions of greenhouse gases.
Willis is even more pessimistic. We wont see ice sheets grow or see the oceans cool for many generations. In fact, sea level is expected to rise for hundreds, perhaps thousands, of years even if carbon dioxide levels could be stabilized immediately.
Most studies indicate the sea level will rise between one and two meters by the end of the century. I know that may not sound like much, but such rises could have devastating consequences. The rising sea level, when combined with waves generated by high winds, storm surge, storm runoff and tides, could put millions of us who live along densely populated coastlines of the United States in harms way. The impact would be the same worldwide.
Given the uncertainty in estimating the amount of future sea level rise, these satellites have become an early warning system. Unfortunately, Jason 2 is nearly 4 years old and was designed to run for only five years. Its successor, Jason 3, has suffered delays due to budget constraints and hasnt been put into orbit. Although much of Jason 3 has been built, its launch date has slipped to spring 2014 at the earliest. Until 2014, lets hope that Jason 2 will continue to send us this vital sea level information.
Todays forecastIt was hot Saturday across the North County with both Paso Robles Airport and Creston reporting 107 degrees at 5 p.m. The record for June 16 in Paso Robles was 115 degrees, recorded in 1961. At around the same time, Avila Beach was fogged in and reported only 59 degrees as gentle southerly winds brought coastal stratus up from the Southern California Bight.
A steeper and shallower temperature inversion layer developed last night. This condition combined with gentle (8- to 12-mph) westerly (onshore) winds produced extensive marine low clouds and fog Saturday night through this morning along the coast.
Temperatures will be about 10 and 15 degrees lower in the North County today. Maximum temperatures in the North County (Paso Robles) will reach the low to mid-90s, while temperatures in the coastal valleys (San Luis Obispo) will range from the mid- to high 70s. The beaches will partially clear during the afternoon and temperatures will be mostly in the 60s.
The coastal stratus will become more widespread Monday, and temperatures will continue to cool to near normal by Tuesday.
Another slight warm-up is forecast for Wednesday and Thursday with slightly above normal temperatures at the coast, and warm to hot temperatures in the North County.
Strong to gale-force (25- to 38-mph) northwesterly (onshore) winds will produce significantly cooler temperatures along with night and morning low clouds and fog next weekend.
Todays surf reportThis mornings 3- to 5-foot northwesterly (310-degree deep-water) swell (with an 8- to 11-second period) will remain at this height and period through Monday.
A 4- to 6-foot northwesterly (295-degree deep-water) swell (with an 8- to 12-second period) will arrive along the Pecho Coast on Tuesday and will remain at this height and period through Thursday morning.
Increasing northwesterly winds will generate a 4- to 6-foot northwesterly (310-degree deep-water) sea and swell (with a 5- to 11-second period) Thursday afternoon and will continue at this height and period through Saturday. Arriving from the Southern Hemisphere: Todays charts and models are indicating fairly quiet conditions in the Southern Hemisphere.
A 1-foot Southern Hemisphere (220-degree deep-water) swell (with an 18- to 20-second period) will arrive along our coastline Wednesday, building to 1 to 2 feet (with a 16- to 18-second period) Thursday into Friday.
Seawater temperaturesThe decreasing amount of upwelling combined with a northerly flowing current has produced warmer seawater temperatures.
Seawater temperatures will range between 55 and 57 degrees through Wednesday, gradually decreasing Thursday through Saturday.
NEXT100 provides an in-depth look at the intersection of the clean energy business and the environment. It focuses on trends in green technology, policy and Earths climate that will most impact the energy industry and our customers over the next 100 years PG&Es second century in operation.
NEXT100 is written and edited by my colleague Jonathan Marshall, with contributions from other colleagues at PG&E. Its now part of PG&E Currents, the companys news website.
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John Lindsey is a meteorologist for PG&E who has lived along the Central Coast for more than 25 years. If you would like to subscribe to his daily weather forecast or ask him a question, send him an email at firstname.lastname@example.org.