Understanding the Role of Satellites in Detecting Sea Level Changes

The Earth's sea levels are changing, and the impacts of these changes are significant for coastal communities and ecosystems. Satellite technology has played a crucial role in monitoring these changes, but its accuracy and effectiveness are highly dependent on the specific mission and instrument used.

Specificity and Accuracy in Satellite Instruments

Not all satellites are designed to detect changes in sea level with the same degree of accuracy. The Jason-3 satellite, for instance, has ocean altimetry accurate to within ±3 cm, even from its orbit of 1330 km above the Earth. This precision is remarkable, but the rate of rise in absolute mean sea level is only between 2 and 3 mm per year, and Jason-3 does not directly measure this mean sea level. Instead, it measures the time it takes for a signal to travel from the satellite to the wave-covered ocean surface and back, then converts this into a distance with an accuracy of ±3 cm. These measurements, when averaged and analyzed, can represent the still water level over a large area over a brief period, although the results come with considerable uncertainty.

Limitations of Satellite Data in Assessing Sea Level Changes

Satellites have insufficient resolution to detect changes in the mean sea level directly. Despite this, researchers continue to rely on satellite altimetry data in efforts to prove an accelerating rate of sea level rise, which is crucial for the theories of anthropogenic global warming (AGW).

For instance, the National Oceanic and Atmospheric Administration (NOAA) reports the rate of rise in the mean sea level from tide gauge stations with two decimal places of accuracy. Tide gauge records can span over a century, such as NOAA's San Francisco tide gauge, which began in 1854. The historical record and higher accuracy of tide gauges make them valuable for calculating the mean sea level and quantifying changes over time. Satellite altimetry data, on the other hand, only goes back a couple of decades and has lower accuracy, making it less reliable for this purpose.

The Debate Over Sea Level Rise

The reliance on satellite data to confirm an acceleration in sea level rise often undermines the significance of longer, more accurate tide gauge records. This contradiction highlights the importance of a comprehensive approach to understanding global climate change. While satellite data provides a snapshot of recent trends, it must be complemented by the long-term, high-precision measurements from tide gauges to paint a complete picture of sea level changes.

The Broader Context: Climate Change Discourse

The discussion around sea level rise and its causes is deeply intertwined with broader debates on climate change and global warming. Advocates of AGW emphasize the need for robust evidence to support their theories and the actions required to mitigate the impacts of climate change. However, the limitations of satellite data in this context highlight the importance of using multiple sources of evidence to draw accurate conclusions about environmental changes.

Conclusion

The debate over whether satellites are the best tool to detect changes in sea level is a complex one. While satellites provide valuable data, they have limitations that must be acknowledged. A holistic approach that incorporates both satellite and ground-based data is essential for understanding and addressing the challenges posed by rising sea levels.