Stories tagged radiation

Sep
20
2011

There’s been some buzz about the relationship between clouds and climate recently, prompting Andrew Revkin of the New York Times’ Dot Earth blog to get his panties in a twist about the “…over-interpretation of a couple of [scientific] papers…”

What gives? I wanted to know too, so I’ve done a bit – ok, a lot – of research and this is what I can tell you: The heart of the discussion is not whether there is a cloud-climate connection (that’s clear), but rather over what that relationship behaves like. There are at least three possible theories, but before we get to those, let’s review some important background concepts.

Gimme the Basics First

Cloud Formation

First, scientists think of air as units of volume called air masses. Each air mass is identified by its temperature and moisture content. Clouds are basically wet air masses that form when rising air masses expand and cool, causing the moisture in the air to condense. You can see the process in action yourself just by exhaling outside on a cool morning. The Center for Multiscale Modeling of Atmospheric Processes has a webpage to answer your other questions about clouds.

Earth’s Energy Budget
Earth's energy budget: Incoming solar energy is either absorbed (orange) or reflected (yellow).  Outgoing energy is radiated (red).  The arrows show the direction and magnitude of movement where thick arrows signify bigger movements.
Earth's energy budget: Incoming solar energy is either absorbed (orange) or reflected (yellow). Outgoing energy is radiated (red). The arrows show the direction and magnitude of movement where thick arrows signify bigger movements.Courtesy NASA

Energy from the Sun is essential for life on Earth. Let’s pretend the Earth has an “energy budget” where solar energy is like money, absorption is like a deposit, reflection is like a transfer, and radiation is like a withdrawal. It’s not a perfect analogy, but it’ll work for starters: Most of the incoming solar energy (money) is absorbed by (deposited into) the ocean and earth surface, but some is absorbed or reflected (transferred) by the atmosphere and clouds. Most of the outgoing energy is radiated (withdrawn) to space from the atmosphere and clouds. The figure to the right illustrates this process.

The Greenhouse Effect

Thanks to the greenhouse effect, our planet is warm enough to live on. The greenhouse effect occurs within the earth’s energy budget when some of the heat radiating (withdrawing… remember our budget analogy from above?) from the ocean and earth surface is reflected (transferred) back to Earth by greenhouse gases in the atmosphere. Greenhouse gases include carbon dioxide, methane, and water vapor. This National Geographic interactive website entertains the concept.

Climate Change

Climate change is occurring largely because humans are adding more greenhouse gases to the atmosphere. More greenhouse gases in the atmosphere means more heat reflected back to earth and warmer temperatures. Warmer temperatures might sound pretty good to your right now (especially if you live in Minnesota and could see your breath this morning as you walked to school or work), but it’s not. Why? Check out NASA’s really great website on the effects of climate change.

Alright, already. What’s the climate-cloud relationship?

From what I can tell, there are three possible theories about the climate-cloud relationship:

  • Clouds actively drive climate change. This is a linear process where clouds reflect too much heat back to Earth, which increases the average global temperature and causes climate change.
  • Clouds passively blunt climate change. This is a cyclical process where more climate change includes increasing average global temperature, which increases average global evaporation, which creates more clouds. More clouds absorb more heat, keeping the average global temperature from rising even faster and lessening climate change. This slows down (note: it does not stop) the rate of climate change.
  • Clouds passively amplify climate change. This is a cyclical process where more climate change includes increasing the average global temperature, which increases average global evaporation, which creates more clouds. More clouds reflect more heat back to Earth, which raises the average global temperatures and worsens climate change. This speeds up the rate of climate change.
  • So which is it? Probably NOT Theory #1. Maybe Theory #2… or maybe it’s Theory #3? Scientists aren’t quite sure yet, so neither am I, but the evidence is stacking against Theory #1 leaving two possible options. The next big question seems to be surrounding the size of the effects of Theory #2 and Theory #3.

    Using what you just read about cloud formation, the earth’s energy budget, greenhouse gases, and climate change (Woah. You just learned a lot!), what do you think? What’s the climate-cloud relationship?

    If you want, you can read more about what scientists are saying about the climate-cloud relationship here:

The ongoing nuclear disaster in Japan has been upgraded to a 7, the highest possible threat level. Authorities say that, despite the potential radiation exposure to people in the surrounding area, the Japanese disaster is still only emitting about 10% of the radiation at Chernobyl. More soon...

I love XKCD. How is it that a comic strip has such good technical explanations? Anyway, here you'll find a chart of the ionizing radiation dose a person can absorb from various sources. Check it out. You'll feel much smarter.

Sep
09
2008

Okay, hold that pose: But we're going to want to try it without... without...  Forget it.
Okay, hold that pose: But we're going to want to try it without... without... Forget it.Courtesy NASA
And they didn’t just have sex; they actually reproduced, which turns out to be important for naked astronauts. But we’re getting ahead of ourselves, aren’t we?

No, we aren’t.

Tiny, naked astronauts were recently exposed to the vacuum environment, harsh temperatures, and dangerous radiation of space for a period of several days. The space travelers went into an almost entirely dormant state for the duration, slowing their metabolisms to .01% of their normal levels.

After they were brought back into the low-orbit space vessel, most of the astronauts were completely revived. (Some died. It was very sad.) Aside from enduring the vacuum of space, and the extreme temperatures outside of a space capsule, the astronauts’ ability to survive the radiation of space most surprised scientists. On the surface of earth, solar radiation (as you no doubt are aware) is strong enough to give us sunburn, and cause genetic damage to our skin cells (leading to skin cancer). The levels of radiation in space are 1,000 times higher, enough to sterilize an organism, yet the astronauts did fine with it, and were even able to successfully reproduce on their return to earth. Scientists hope to isolate whatever mechanism allowed the astronauts to repair the genetic damage they likely incurred while in space. Such research might be applied to radiation therapy techniques.

We salute you, tiny, naked challengers of the unknown.

Science stares inside
Science stares insideCourtesy Nevena
Researchers in Belgium have figured out why apples stay crunchier, after being picked, than pears. Micro structures through out the fruit of an apple are able to deliver oxygen to the cells while the structures in pears are dense and closed off which prevents oxygen flow. These scientists determined this by using a high tech radiation facility to create images of the internal structure of the fruit. But, you can get a sense for their findings yourself at home. Drop and apple and a pear in a jug of water. Find out which on sinks? Can you think why?