# Understanding the Science of CO2’s Role in Climate Change: 1 – Introduction

Moving Beyond Trend Charts

I have made many trend charts and regressions over the past 4 years as I try to learn as much as I can about climate change and CO2’s role in global warming. Here are links to some of my previous Climate Charts & Graphs work:

While these trend charts and regressions help to show the relationships between climate factors, I keep asking myself the fundamental question “how does atmospheric CO2 actually affect the earth’s temperature”. To answer this, I need to delve more deeply into the physics of CO2 in the atmosphere to really understand the CO2 – climate change relationship. As I read climate science papers and visit climate change websites, I get a sense for the physics of CO2 and climate change, but not a real solid understanding.

David Archer’s “Global Warming, Understanding the Forecast book and accompanying videos of his Chicago University lectures and Dennis Hartmann’s “Global Physical Climatology have helped my understand the role that solar radiation, electromagnetic spectrum, blackbody radiation,  Stefan-Boltzmann Equation, Planck’s Law,  atmospheric absorption bands and greenhouse gases play in the global energy balance and climate change.

To really understand CO2’s role, I need to work with the numbers and formulas myself so that I can see the cause and effect relationships. I have developed a series of Excel tools to help me understand the physics behind global warming and to be able to reproduce several of the critical charts necessary to understanding climate change.

This series of posts will outline and graphically display the key topics and present the Excel tools that I found helpful to me to understand basic climate change science.  Where possible, I present downloadable Excel workbooks to let readers work with the fundamental equations and check out the basic mathematical relationships for themselves.

In this previous post, I discussed total solar irradiance (TSI) trends since 1611. I’d like to show how the TSI, also known as Solar Constant,  is actually calculated.

The Earth receives essentially all of its energy from the sun’s (link) thermal radiation striking the surface of the Earth. The Sun emits energy at the rate of 3.839 x 1026 Watts (W) (definition). As shown in the schematic below, the Earth receives approximately 1,367 W/m2 at the top of the atmosphere (TOA) from the Sun. This so called solar constant is actually not constant; its value depends on the distance between the Sun and the Earth, which changes because of the Earth’s elliptical orbit.

The total solar energy striking the Earth is equal to the area of the Earth perpendicular to the Sun’s rays  times the Solar Constant (Sd). At the top of the atmosphere (TOA), the average incoming solar energy per unit of surface area of the Earth equals the solar energy striking the Earth Se-in divided by the entire surface area of the Earth (Ae ), 342 W/m2.

Not all solar energy at the top of the atmosphere reaches the Earth’s surface; some is reflected by clouds and the Earth’s surface. The next post will  discuss the global energy balance, what happens to the solar energy as it travels from the TOA to the surface, the Earth’s thermal radiation and how the Earth maintains thermal equilibrium.

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