How much solar energy hits the Earth?

The earth is a solar-powered planet but instead of using the Sun for power, we drill for dead animals. In the morning, as we wake up, the sun glances over the horizon to shed light on us, blanket us with warmth and provide energy to start our day. Our sun’s "juice" drives our planet’s ocean currents, seasons, weather, and climate. Without the Sun, life on Earth would not be possible. For nearly four decades, NASA has been measuring how much sunshine powers this planet.

“You can look at the earth and sun connection as a simple energy balance. If you have more energy absorbed by the Earth than leaving it, its temperature increases and vice versa,” said Peter Pilewskie, a TSIS-1 lead scientist at the Laboratory for Atmospheric Physics (LASP) in Boulder, Colorado. Under the direction of NASA, LASP is giving and administering the instrument’s measurements to the scientific community. “We’re measuring all the radiant energy that is coming to Earth.”

But it’s not really this simple.  The sun’s output energy fluctuates considerably. Over the course of about 11 years, our sun cycles from a relatively tranquil state to a peak in intense solar activity — like explosions of light and solar matter — called a solar maximum. In succeeding years the sun returns to a quiet state and the cycle starts over again. The sun has fewer sunspots — dark areas that are sometimes the source of increased solar activity — and stops producing so many explosions, going through a period called the solar minimum. Over the course of one solar cycle (one 11-year period), the sun’s released energy varies on average at about 0.1 percent. That may not sound like a lot, but the sun emits a large amount of energy – 1,361 watts per square meter. Even fluctuations of merely a tenth of a percent can affect the earth.

Variations in the solar cycle

Solar cycles can deviate from decade to decade. Scientists have observed unusually quiet magnetic activity from the Sun for the past twenty years with previous satellites. During the last prolonged solar minimum in 2008-2009, our Sun was as quiet as it has been observed since 1978. Scientists expect the Sun to enter a solar minimum within the next three years, and TSIS-1 will be primed to take measurements of the next minimum.

Scientific data is also critical for understanding the earth's climate through models. Scientists use computer models to interpret variations in the sun’s energy input. If less solar energy is available, scientists can calculate how that will affect earth’s atmosphere, oceans, weather and seasons by using computer simulations. The input from the sun is just one of many factors scientists used to model the earth’s climate. Earth’s climate is also influenced by other factors such as greenhouse gases, clouds scattering light and small particles in the atmosphere called aerosols — all of which are considered in comprehensive climate models.

TSIS-1 will study the total amount of solar radiation emitted by the sun using the Total Irradiance Monitor, one of two sensors on the instrument. The second sensor, called the Spectral Irradiance Monitor, will gauge how the sun’s energy is distributed over the ultraviolet, visible and infrared regions of light. TSIS-1 spectral irradiance measurements of the sun's ultraviolet radiation are critical to understanding the ozone layer — earth's natural sunscreen that protects life from harmful radiation.

“Knowing the sun’s behavior and knowing how earth’s atmosphere responds to the sun is even more important now because of all the different factors that affect climate change. We need to understand how all of these interact on earth’s system,” said Pilewskie.

The time to transition to solar energy is now. Please see our informative blog for more information about the specifics of installing solar energy.

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