55 Music Concourse Dr.
Golden Gate Park
San Francisco CA
Regular Hours:


9:30 am – 5:00 pm


11:00 am – 5:00 pm
Members' Hours:


8:30 – 9:30 am


10:00 – 11:00 am

Please note: The Academy will be closing at 3:00 pm on 10/24 (final entry at 2:00 pm). We apologize for any inconvenience.

There are no notifications at this time.

Climate Change 

January 30, 2007

Controlling Earth’s Climate

The Earth’s climate is all about energy at or near the surface of the planet. So anything that affects this energy will influence climate. Some of the major influences include:

  • Solar insolation, or the amount of energy that reaches us from the Sun. This amount varies over very long timescales (e.g. the Sun has gotten brighter as it ages) and very short, annual time scales.
  • Earth’s orbital geometry. The Earth is tilted on it’s orbital axis, and also wobbles as it revolves. The amount of tilt and wobble vary over tens of thousands of years, and these quasi-cycles are called Milankovitch cycles. These variations affect the amount of sunlight that reaches various areas of the Earth’s surface.
  • Continent/ocean configuration. The contiguity and orientation (north-south, east-west) of the oceans affects their circulation, and ocean circulation is probably the most important surface influence on climate. The amount of continental landscape exposed (i.e. not submerged) is another major influence. Land heats up and cools down much more quickly and easily than does water.
  • Volcanism and other tectonic activity. Volcanic activity can cool the planet down by spewing masses of particles into the upper atmosphere and shading out the Sun. The recent eruptions of Mt. Pinatumbo in the Phillipines is a great example of this. Volcanism can also release greenhouse gases though, such as carbon dioxide, and hence warm up the planet.
  • And last but not least, the biggie that we are interested in, greenhouse gases. Greenhouse gases have the interesting property of being permeable to incoming solar radiative heat, but reflective of outgoing radiative heat from the Earth. Solar heat is high energy ultraviolet radiation. It passes through the atmosphere and warms up the surface during the day. Later on, the Earth’s surface radiates it out into the cooler atmosphere, but now as lower energy infrared radiation. Greenhouse gases trap a lot of this radiation, and hence, more heat enters the Earth’s system than leaves it. This is very important! If we did not have sufficient levels of greenhouse gases, Earth would be a brutally cold desert like Mars. Unfortunately, too much of these gases, and you have a runaway greenhouse hothouse like Venus.

Now, think of all these mechanisms acting at the same time. Each one affects climate in some way. But it’s not a simple problem of adding up all the influences. These mechanisms can interact with each other. Sometimes they reinforce each other, sometimes they cancel, and how they interact can be affected by numerous other physical, chemical and biological processes. These are so-called feedbacks. Beginning to understand why climate science is so complex? One of the big challenges that scientists face today is to understand how these mechanisms behave over time and under various circumstances, how they may or may not interact, and what influences them. Some of the answers are easy; e.g. nothing here on Earth has much of an influence on what the Sun is doing. But guess what? A LOT of what goes on here on Earth can affect some of the other mechanisms. Can you figure out which one is most easily influenced? If you said greenhouse gases, then you are correct! In my next posting, we’ll talk about greenhouse gases, what they are and where they come from.

Filed under: Climate Change — Peter @ 9:20 pm

January 28, 2007

The Facts of Climate Change

So what is this Climate Change problem all about? This is actually a very difficult question to answer, because the answer is part science, part economics, part politics, and part human nature. In the next few entries I’ll run through some of the basics of the science behind climate change, the things that we understand, and the things that are still uncertain. But first, let’s review some facts:

1. Earth’s climate has been changing very rapidly over the last few decades.
2. This climate change is driven largely by climbing global temperatures.
3. Global temperatures are climbing because of the tremendous increase of greenhouse gas concentrations in the atmosphere over the last 150 years.
4. The rapid increase of greenhouse gas concentrations is, overwhelmingly, the result of increased human industrialization and utilization of carbon-based fossil fuels.

These are solid observations and cannot be disputed on scientific grounds. In the next entry we’ll get a quick primer on the Earth’s climate! In the meantime, you can take a look at Wikipedia’s excellent entry on the topic (Wikipedia:Climate Change), though as with all Wikipedia entries, remember that there are numerous authors and opinions.

Filed under: Climate Change — Peter @ 11:27 am

January 26, 2007


This is my first posting on this Academy blog. I am Dr. Peter Roopnarine, the Curator of Geology and Paleontology here at the Academy. I am an interdisciplinary biologist and earth scientist with a variety of research interests. Originally, a lot of my work involved the study of extinctions of marine organisms over the last 35 million years, and evolutionary recovery from those extinctions. More recently I’ve become interested in Earth’s current biodiversity crisis, the ongoing extinction of species, and what we can learn about it from extinctions in the fossil record. This has all lead to a growing interest in modern climate change and global warming.


Modern climate change is most likely the largest issue that has ever faced humans, and we need to understand it. In this blog, I’ll try to explain some of the basic science of climate change, and take a critical look at the almost daily reports and comments that are flooding the media these days. Climate change is a problem caused by the collective actions of millions of people, including you and me, and it will only be solved by our collective understanding and positive choices.

Filed under: Climate Change — Peter @ 11:51 pm

Academy Blogroll