From the AGU EOS publication (h/t to Dr. Judith Curry)
Better Data for Modeling the Sun’s Influence on Climate
Compared to other stars, our Sun is a remarkably steady source of light and heat, but its output does vary. Solar light, heat, and particle streams drive weather and atmospheric chemistry, but how (and how much) does the Sun’s variability affect the climate here on Earth? The role of solar variability in recent global warming is not just a bone of contention; it is also a question of overriding importance for the scientific understanding of our Sun and of climate change.
Scientists simulate historical and future climates by setting up a suite of initial conditions and seeing how these conditions change when various factors, called forcings, are applied. For example, how does Earth’s surface temperature change if it receives more or less heat from the Sun? How do the streams of ionized particles that make up the solar wind affect certain weather patterns on Earth? Data sets compiled from historical records provide the necessary information for model forcing, so ensuring that these data sets provide accurate, relevant information is key to producing realistic climate model scenarios.
Recently, a series of initiatives brought together scientists working on different aspects of this highly multidisciplinary issue. These efforts shared several common objectives, including better estimates of solar forcing and identifying and quantifying the uncertainties in these estimates.
Here we report on the outcome of three of these initiatives:
- “Towards a more complete assessment of the impact of solar variability on the Earth’s climate” (TOSCA), a project that uses a network of European scientists from 20 countries that met from 2011 to 2015 to assess contributions of solar variability to Earth’s climate
- Solar Irradiance Data Exploitation (SOLID), a European-funded project dedicated to merging all exploitable spectrally resolved solar irradiance records into one single composite data set
- An international team of scientists that met at the International Space Science Institute (ISSI) to produce a comprehensive data set that includes solar radiative forcing and contributions from energetic particles
These initiatives have culminated in the production of two public data sets to assist with the scientific analysis of solar forcing: a composite data set of all irradiance observations and a comprehensive data set containing different solar forcings (radiative and by particles) since 1850.
How Does Solar Variability Affect Climate?
Solar variability affects Earth’s climate in many intricate and nonlinear ways. Most effects are ultimately driven and modulated by the solar magnetic field and its conspicuous solar cycle, which repeats approximately every 11 years.
The effect of solar variability on climate is mostly hidden in the natural variability of the climate system; thus, careful statistical analysis is required to extract it from a noisy background. Such analyses require records that extend over a long period of time, but the paucity of observations in existing records poses a serious challenge. For example, scientists have been making direct measurements (from space) of the total solar radiative input into Earth’s atmosphere only since 1978, although there had been earlier attempts to measure it from the ground.
Full story at EOS here