All posts by Robert Cahalan

Dr. Robert Cahalan is Director of Sun-Climate Research at NASA’s Goddard Space Flight Center in Greenbelt Maryland.  He recently retired as Chief of Goddard’s Climate and Radiation Laboratory, and President of the International Radiation Commission.   He has held several jobs related to climate change, and has been doing science research for more than 40 years. He loves science, building scientific instruments, and using them to discover how the universe works.  Bob says: “Clouds are endlessly fascinating for their many complex and beautiful properties, and important for Earth’s climate because they control the flow of energy in the atmosphere, and the supply of energy to the oceans. At Goddard I designed a laser system with multiple views, like a bee’s eye, showing that it can see through clouds to measure their thickness, naming it THOR, for ‘Thickness from Offbeam Returns.’ I have flown THOR over Oklahoma, Central America, and Antarctica, measuring clouds, ice, and snow. I discovered that clouds have an ‘effective thickness’ depending on their fractal properties, an idea now used in global climate models.“

My visit to European Geophysical Union in Vienna

I am a “guest” here, invited by my longtime friend Sadri Hassani, with whom I studied physics at U. of Illinois – Urbana, back in the 1960’s. Sadri, thanks very much for inviting me!  I’m posting this from a hotel room in Vienna, Austria, where I’m attending the “European Geophysical Society” meeting to give an invited talk about “Total Solar Irradiance” or “TSI”, or what used to be called the “solar constant” which is now being measured very accurately by NASA’s “Solar Radiation and Climate Experiment” (SORCE) for which I’ve served as the Project Scientist for 15 years. As a result of SORCE, we now know that the Sun’s TSI value is about 0.5% lower than the value accepted since the 1990’s. That means that the solar luminosity is also 0.5% lower, which increases the best estimate of the Sun’s lifetime from about 10.7 billion years to 10.75 billion years, giving us an extra  50 million years to figure out how to escape the solar-driven holocaust that is expected once the Sun ceases to fuse hydrogen into helium. Actually, the worry of what may happen to mankind when the Sun goes nova, in about 5 billion years, is not nearly as pressing as the worry of what may happen in the current decade of history, due to fossil fuel consumption, and the twin consequences of global warming and ocean acidification, about which I’ll write more in future posts. But now I’ve got to sign off, and say Auf wiedersehen! from here in Vienna.