Measurements at the Mauna Loa Observatory stopped after the 2022 eruption of the Mauna Loa volcano, when lava flow crossed the access road and took out power lines to the facility. The observatory remains inaccessible by vehicle and without power from the local utility company.

Observatory staff has established limited solar power in four observatory buildings and restored approximately 33 percent of the measurements onsite, including the Global Monitoring Laboratory and Scripps critical CO2 records and other atmospheric measurements.

Media can contact: Theo Stein (303) 819-7409 ( or Karin Vergoth 303-632-6413‬ (


NOAA logo National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory (ESRL)

What does this program measure?

Total Downwelling solar and thermal infrared radiation (or irradiance) is measured in units of Watts per square meter. Aaerosol optical depth is also measured.

*** The Mauna Loa Observatory record of solar transmission of sunlight is the longest continuous record of this nature in existence.

How does this program work?

We primarily use commercial thermopile broadband radiometers to measure the irradiance and aerosol optical depth, a measure of the total dust and particle load of the atmosphere, is measured with a sunphotometer.

Measurement Instruments Frequency Site
Global Irradiance Eppley Pyranometers with Q, OG1, and RG8 filters continuous MLO
Direct Irradiance Eppley pyrheliometer with Q filter(2) continuous MLO
Direct Irradiance Eppley pyrheliometer with Q, OG1, RG2, and RG8 filters 3/day
Direct Irradiance Eppley/Kendall active cavity radiometer continuous MLO
Diffuse Irradiance Eppley pyrgeometer with shading disk and Q filter (2) continuous MLO
UV Solar Radiation Yankee Environmental UVB pyranometer (230-320 nm) continuous MLO
Diffuse (IR) Irradiance Terrestrial downwelling IR pyrgeometer with shading disk continuous MLO
Column Water Vapor 2 two-wavelength tracking sunphotometers: 860, 940 nm continuous MLO

Why is this research important?

Solar and infrared radiation are fundamental ingredients in maintaining the current climate, and also play a major role in anticipated changes in that climate. Aerosol optical depth helps quantify the role of aerosol in radiatively forced climate change.

Are there any trends in the data?

Read a MLO Solar Irradiance publication (.pdf format)

While no persistent long-term trends have been detected, there are excursions of several years in duration following major volcanic eruptions and there appears to be increased springtime aerosol loading in the last few years.

As the plot below shows, aerosols from large volcanic eruptions block some sunlight from reaching the earth's surface. Note how the lidar measurements of the volcanic aerosols in the stratosphere anti-correlate with the solar record.

MLO Solar Radiation Transmission

How does this program fit into the big picture?

What is it's role in global climate change?

Solar and thermal infrared (IR) radiation are vehicles for climate change but at the same time are affected by that change. Our radiation measurements can be used to investigate both the causes of and the response to climate change.

Comments and References

  • Dutton, E. G., J. J. DeLuisi, and A. P. Austring, 1985. Interpretation of Mauna Loa
  • Atmospheric Transmission Relative to Aerosols, Using Photometric Precipitable Water Amounts. J. Atmos. Chem., 3, 53-68.
  • Dutton, E.G., 1992. A Coherence Between the QBO and the Amplitude of the Mauna Loa Atmospheric Transmission Annual Cycle. International J. Climatology 12, 383-396.
  • Dutton, E.G. and J.R. Christy, 1992. Solar Radiative Forcing at Selected Locations and Evidence for Global Lower Tropospheric Cooling Following the Eruptions of El Chichón and Pinatubo. Geophys. Res. Lett. 19, 2313-2316.
  • Dutton, E.G., P. Reddy, S. Ryan, and J.J. DeLuisi, 1994. Features and effects of optical depth observed at Mauna Loa, Hawaii: 1982-1992. J. Geophys. Res. 99, 8295-8306.
  • Dutton, E.G. and B.A. Bodhaine, 2001: Solar irradiance anomalies caused by clear-sky transmission variations above Mauna Loa 1957-1999. J. Clim., 14, 3255-3262.
Lead Investigator(s):

Dr. Ellsworth Dutton
Jim Wendell

MLO Contact(s):

Paul Fukumura
808-933-6965 (x223)

Web Site(s)

Date Started


Related Programs

Solar Radiation

MLO Solar Dome
Solar dome
Solar Dome In Open Position
Open solar dome
UVB Equipment in Dome facing Sun
Tracking the sun
Eppley Solar Tracker
Diffuse irradiance
Top of Solar Filter Wheel
Top of filter wheel
UV Sensors facing Mauna Kea
Quartz global pyranometer
solar radiation sensor closeup
OG1 global pyranometer
ESRL Kipp Zonen Solar Instrument
Kipp & Zonen tracker
Solar deck from top of MLO tower
Solar deck from top of MLO tower