The Norwegian Academy of Sciences is located in Drammensveien 78, at walking distance from the city centre.
From the Oslo airport in Gardemoen ( www.flytoget.no/eng/ ) the best option is to take the airport express train to the station Nationaltheateret (which is the next stop after Oslo Central Station).
From Torp airport in Sandefjord ( www.torp.no ) or Moss airport in Rygge (www.ryg.no ) there are bus connection arriving to the Oslo bus terminal close to the Oslo Central Station.
Once in town, tram 13 towards Jar/Lilleaker passes by both the Central Station (Jerbanetorget in Norwegian) and the Nationaltheatret station. Website of public transport: ruter.no/en/
The Academy of Sciences is in between the two stops Skillebekk and Skarpsno.
To give dimensions, please note that the walk from Nationaltheateret to the Academy is about 25 minutes long.
Please make sure that you have valid tickets for the tram. Tickets can be bought at vending machines in Oslo Central and Nationaltheateret (silver coloured), or in kiosks at these train stations. You can also buy from the tram driver, but these tickets are significantly more expensive.
Connections with the Gardemoen airport via taxies are possible, note that the fares depend on the taxi company and are subject to changes depending on the day (week day/weekend) and the time of travel (day/nigh). Fares range in the surrounding of NOK 700 – 1000. See avinor.no/flyplass/oslo/til-og-fra-flyplassen/tog-buss-og-taxi/#!taxi-872
An interactive map can be found here: www.cas.uio.no/contact/map.php
Weather in Oslo
Also if you wonder about the weather in Oslo, then you can read it here: www.yr.no