21 April 2008

Math, Science, and Engineering, oh my

Since I've studied all three, and appreciate all three, it always surprises me when people try to claim that they're not different.  Usually this is a math or engineering person trying to say their area is science.  This is, well, just wrong, I think.

One area of confusion is that each is a matter of what you're doing at a given time.  One can easily have a job which carries one label, but be doing on of the other things.  My job title, for instance, says that I'm a scientist, but much of what I actually do is what I consider engineering.  No problem to my psyche as I respect engineering.  The only question then is whether I can do good engineering.  Conversely, some with a job title of engineer may at times be doing science.  What matters to me is not the title, but what one does.

The main divider between the three, as I see it, is how do you decide that you're right (or, have done good math, science, or engineering).  In mathematics, you work within a rigorous framework and prove that you are correct (that a theorem you or somebody else proposed is either true or false).  You might have made an error in your proof, and the decision on that is made by other mathematicians.

Science and engineering both appeal to nature, rather than scientists and engineers.  The scientists compare the predictions of their theory to the observations.  If they're close enough, then the theory is considered good enough.  It isn't proven.  Next year we might have more and better observations, and the theory might not agree well enough any more.  A different side is, scientists can think of highly idealized systems (frictionless surfaces, massless strings, point masses, ...) which don't actually exist in nature.  If the predictions are close enough, however, then the science is good.

Engineering, does appeal to nature (did the bridge hold up?), but has very limited degrees to which it can simplify its systems (real bridge beams vary in their properties, while ideal ones don't, and the difference can crash the bridge).  The more significant distinction from science goes back to the matter of how you decide you've done good engineering.  Engineering, I take it, is the application of a knowledge of science to achieve a useful end.  But who decides useful?   Somebody, somewhere, writing the checks to support the project.  It would be very easy to 
build a several mile long bridge, for instance, if your budget were unlimited and so were the time for construction.  But for real engineering, you have serious limits on time and money.  How do you build a bridge fast enough and cheap enough, while still carrying the required load?  That's an engineering challenge.

20 April 2008

No running in thunderstorms

Blogging instead of running right now. I run through almost all weather, including rain, snow, sleet, -10 F temperature, -30 F wind chill, temperatures over 100 F, etc. The one type of weather I won't run in is thunderstorms. It isn't strong now, but I'm still hearing occasional thunder.

Thunder means lightning, and lightning is bad for my health. Plus, I can't outrun lightning.

11 April 2008

Sorts of ice age

In addition to there being types of ice, there are types of ice age. Again this seems odd, but again the differences become important if we try to understand the climate. Depending on which of the three types of ice age we're concerned with, the answer to the question 'Are we in an ice age now?' is either no, we've been in one for 2.5 million years, or we've been in one for about 35 million years.

The first type of ice age is probably the most familiar. It really is asking 'Is there a whole lot of ice in the northern hemisphere?'. A little more specifically, it is about how much ice mass there is. While the area of snow cover and sea ice cover can be large, we don't think of that as being an ice age for this type. The ice age for this is when most of Canada and the northern USA are under 1-2 miles (1-4 km) of ice. The last time we were in that sort of ice age was about 15,000 years ago, give or take. Certainly we were done with it by about 7,000 years ago. Call this ice age type 'ice burying Chicago'.

The next sort is the 'ice burying Greenland' ice age. We've been in that condition continually since about 2.5 million years ago. Greenland is larger than Texas or France, so counts for having some significant size. The question here is 'Is there substantial ice anywhere in the northern hemisphere?' Before about 2.5 million years ago, back to over about 250 million years ago, the answer was no.

Those two types of ice age are biased towards an interest in the northern hemisphere. Since I, and most of the world's people, live in the northern hemisphere, I'm not entirely opposed to the bias. But, since I also am concerned about ice and ice sheets in their own right, let's consider the more general question for ice age 'Is there substantial ice anywhere on the planet?'
The answer to this is yes, and has been so for about 35 million years. Antarctica, sitting down on and around the South Pole, has had substantial ice since about then.

Now it isn't the case that we always have lots of ice somewhere on the earth. Prior to that 35 million years ago, you'd have to go back more than another 200 million years to find an ice age by the third definition. Over the history of the earth, it appears that ice ages are an unusual condition for the earth. Most of the time (over 80% in fact), the earth doesn't have any significant ice. Obviously to see it this way, we have to be taking a very long view of the earth's history.

For thinking about current climate, then, we want to be careful about what sort of ice age we're talking about. Some people refer to us 'still coming out of the ice age'. They're wrong for all three sorts of ice age. We were done coming out of the last 'bury Chicago' sort of ice age 7,000 years ago. And we're still in the other two sorts. If they were to end, sea level would rise by about 7 meters (about 20 feet) for the 'ice in the northern hemisphere' ice age, or about 70 meters (over 200 feet) for 'ice in the world' ice age. Since some hundreds of millions of people live less than 20 feet above sea level, I'd rather not come out of even just the northern hemisphere sort of ice age any time soon.

04 April 2008

Types of ice

It sounds a bit odd to be talking about 'types' of ice. But media and net articles have included enough confusion that I've decided it's actually an important point.

Ice shows up in many parts of the climate system and is generally important when it does. So I'll describe the types of ice before getting in to the confusions. (Aside: the science that studies ice is glaciology).

In the atmosphere, ice crystals high in clouds can be important for starting rain formation. Of course ice falling from the sky, whether as snowflakes, ice pellets, or hail, can be important to know about as well.

On land, one of the less well-known ice types is permafrost -- ice that is in the soil and persists from year to year. This mostly happens in very cold areas such as northern Alaska, Canada, and Siberia. For more detail about permafrost, see the National Snow and Ice Data Center's (NSDIC) page http://nsidc.org/sotc/permafrost.html They also include a graphic of where you can find permafrost. In recent years, permafrost extent has been decreasing. Since ice is a somewhat hard material, this causes problems in areas where buildings and roads were built on top of permafrost.

The two better-known land ice types are glaciers and ice sheets. Glaciers are the ice that sits on mountains. The fact that they're on sloping surfaces is important for how they move. Again, the NSIDC has an introduction to glaciers, this one aimed better towards students than the permafrost. Ice sheets are the enormous masses of ice on land. They're so big that they swamp mountains and mountain ranges. Now there are only two ice sheets -- the Greenland and the Antarctic. Sometimes we talk of the East and West Antarctic ice sheets because a mountain range (the Transantarctic mountains) runs through the Antarctic ice sheet and does fairly well separate the flow of ice. During the last ice age, there was a large ice sheet across most of northern North America, called the Laurentide ice sheet. Both ice sheets are losing mass, as are most glaciers. One reason for concern about this is that as the ice melts, its meltwater flows into the ocean and raises sea level.

On water we have three different types of ice to think about. Perhaps the oddest is ice shelves. This is ice that is floating on water, but which is attached to ice on land. The land part feeds the floating part. Several Antarctic ice shelves have collapsed into the ocean in the last few years. Icebergs are what we get when a chunk of an ice shelf breaks off. They can be as large as cities and small states or countries. The large ones, though, are in the Antarctic only. The Greenland icebergs are much smaller, though more than enough to sink the Titanic. The International Iceberg Patrol monitors the locations of these North Atlantic icebergs.

The last happens when the water freezes -- sea ice. Sea ice floats and gets moved by winds and water currents. It is important for predicting the weather, so you can see today's coverage at the NOAA/NWS Marine Modeling and Analysis Branch web page. Last fall, the Arctic experienced a record minimum in its extent at the end of the summer. The NSIDC has collected information about the record at http://nsidc.org/news/press/2007_seaiceminimum/20070810_index.html On the other end of the earth, the Antarctic ice pack has been showing a small increase in its extent, see the Crysophere Today for information about the anomaly (how much more or less ice there is compared to what's normal for the time of year) in ice coverage for both the Arctic and Antarctic. (The Antarctic is at the bottom of the page.)

So now for the confusions some have had. When our concern is about sea level, the type of ice we care about is land ice -- the ice sheets and glaciers mostly. When these types melt, sea level rises. If all of the Greenland ice sheet melted, sea level would rise about 6 meters (about 20 feet), enough to put much of Florida, for instance, below sea level. Glaciologists have observed that both Greenland and Antarctica ice sheets are melting. A research question is just how fast they will melt in the future. Most glaciers are also melting.

That's straightforward. What some have confused is 'Antarctic ice', where they're thinking about sea level changes (so should be concerned about land ice) and then looking at the sea ice instead. Sea ice has little to do with sea level. In terms of total sea ice trends, you can look again at Crysophere Today and compare how large the Antarctic positive anomaly is to the Arctic negative anomaly.

A different confusion was someone who compared the February ice cover in the Arctic (near the time of its maximum extent -- it's cold in the Arctic in the winter!) to the cover last fall (near the time of minimum coverage -- after the summer's heat had time to melt as much ice as it could). When we're looking for changes for climate, we certainly have to pay attention to what time of year it is!

If anyone says there's more (or less) ice, be sure that they know which type of ice they're talking about. Also check that they're comparing the same time of year.

01 April 2008

Starting notes

I'm getting started in the blog world, so suggestions are welcome for topics. In addition to my professional areas, I've also done things like science fair judging so might have some ideas there too.

A word about the address of the blog -- moregrumbinescience.blogspot.com. The thing is, my sister beat me in setting up her blog, grumbinescience.blogspot.com. Hers is focused on her jr. high science class. I expect to be covering more levels of science and more general than a particular class. On the other hand, if you're one of her students, you can still post a question or comment here! (I was in class last fall.)