Deserts have apparently been getting bigger

[Gonzolo]

I am looking for maps of the various deserts of the world at different periods in history, especially the last 5000-15,000 years. There are nice color-coded maps of the world today, but I'm curious about the world's surface say, 5000 years ago. Thanks.

 

[Astronuc]

Reasonable maps may only go back about 2500 yrs - to Egypt and China - although David Rohl apparently found some carvings in Egypt going back about 5000 yrs (http://www.nationmaster.com/encyclopedia/David-Rohl). Rohl apparently has some controversial theories.

Also check out this site for subjects in archeology - http://www.pibburns.com/archaeo.htm

You might want to look into paleoarcheology or paleogeology.

 

[Andre]

Well, between 20,000 and 5,000 years ago the climate in Africa changed rather dramatically. The Sahara was a desert 18,000 years ago but changed into a green forest and then back to desert some 5000 years. Lake Victory did not exist before 12,000 years ago and emerged simultaneously with the glaciers of the Kilimanjaro. North Australia was forested 12,000 but then changed into arid savannah steppe as apparently the monsoon failed.

Similar large climate changes happened all around the world. Most of those events are not really consistent with the alleged sudden emerge out of an ice age some 15,000 years ago as some areas seemed to have cooled rather than warmed, like the southern part of South America.

 

[Gonzolo]

What I have in mind are not maps that were drawn 2500 years ago (although that would be neat too), but rather maps made today, that reconstruct the world at that time, using mathematical models or whichever other methods used (possibly including data from actually ancient maps). Do any present day climatologist, environmentalist or geographer bother to do this? I'd like somekind of visual representation of what Andre just said.

 

[Astronuc]

NASA, and possibly some other departments, have been using remote sensing - e.g. ground penetrating radar (GPR). Somewhere I have some articles on the technology. Basically, radar of different wavelengths from high altitude aircraft or satellites can penetrate the ground at different depths - several meters to 10's of meters. The underlying strata can be distinguished and patterns do emerge.

I seem to remember North Africa and the Middle East have been scanned, but I would have to dig around my archives.

 

[Andre]

The most common means of establishing the paleo climate in a given area is draw a lacrustine (lake sediment) core and investigate the bio remains, especially pollen. http://www.landcareresearch.co.nz/research/biodiversity/forest/past_env/pollen_interpretation.asp is a random example.

Loads of links http://www.ngdc.noaa.gov/paleo/pollen.html but they don't always work.

 

[Gonzolo]

Yeah! Wow! I never knew pollen could be so interesting. That BIOME project seems like another important key word. I'll look into what NASA is doing too. Thanks guys.

 

[Bystander]

---and for your viewing pleasure, http://www.scotese.com/paleocli.htm . Dunno how far I'd trust this as absolute, incontrovertible fact, but it is an animation of interpreted data.