# Presentation: 510281

## Big Bear Solar Observatory

**Philip R. Goode**
**Big Bear Solar Observatory**
**New Jersey Institute of Technology**

**Irradiance Changes**
- Blue curve is solar cycle
- Red curve adds purported long-term variation
- Temperature changes from NCAR model
- Yellow line limit from physics of irradiance change

- Big Bear Solar Observatory

**Notes:**
The upper blue curve shows the irradiance variation assuming variations in the past track those over the last two cycles and the red curve includes the putative long term component.  Note that from here on we take the terrestrial perspective in which the mean irradiance is about 340 watts/m2.  This is translated to temperature changes using the NCAR model (paper by Foukal, North and ).  With the long term trend, one can account for part of the cooling over the first half of the 20th century and the depths of the Maunder minimum.  Foukal et al deny the presence of the long-term component on phenomenological grounds (the magnetic network discovered by Hale in the 1890s would have disappearing during the 1920s.  Now that we understand the physics of irradiance change, we can put a hard lower limit on the irradiance change (yellow line).  Increases in irradiance are bound directly by  increases in activity.  Since higher activity cycles are shorter and there is Greenland ice core data showing a roughly cycle going back 100,000+ years, it is unlikely that the Sun’s irradiance over historical times was much  greater than it is now.  Thus, we are left with a mystery...how can there be terrestrial signatures of the solar cycle when the irradiance changes are too small to matter?

## Origin of Sun’s Variable Output

**Seismic data from SoHO/MDI provide most precise measure of solar variability**
**Physical picture is that rising solar activity blocks heat and convective flows, while corregating the solar surface making it a more effective radiator**
**Active sun is cooler, corregated, slightly smaller and more irradiant**
**Inactive sun is warmer, smoother, slightly larger and minimally irradiant**

- Big Bear Solar Observatory

**Notes:**
From these results we are left with a solar role in climate that is more subtle with changes in the solar wind/magnetic field somehow linking with something terrestrial leaving the Earth’s global albedo as the best place to look for a solar cycle.

## Implications of Limit

**Earth is responding to more subtle changes in Sun, which imprint the solar cycle and longer term wanderings of solar activity**
**Changes in solar wind induces some unknown changes at the Earth**
**A new burden on the climate models**

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## Can Earth’s Reflectance Increase while Earth Warms?

**Earthshine and other results point to an increasing reflectance over the past five years, which reverses a fifteen year trend of decline**
**Taken in isolation, less sunlight would imply a reversal of global warming**
**Recently updated NASA ISCCP data reveal a change in clouds, so both reduced sunlight and increased global warming are possible**
**Results also confirm earlier Earthshine results of an increasing Earth albedo**

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## Cloud Amount & Distribution

**Cloud Amount from ISCCP**
**Five year Bands of higher clouds (red) and lower clouds (blue)**
**Unexplained change in last five years**

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## Earth’s Reflectance in Time

**Earthshine (blue)**
**Regression from ES and ISCCP (shaded area)**
**Global reflectance from reconstruction**
**Global warming since 1850 (red)  **

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## Earthshine Plus ISCCP Conclusions

**Earth’s Reflectance has increased over the last five years **
**Clouds have re-arranged themselves in the same period so that their net cooling effect is reduced.  **
**Earth can warm with less sunlight**

- Big Bear Solar Observatory