Dear Lucy,
Climate change is not yet a factor in Goan migration. It might well be in the decades ahead. Goa has a history of migration dating back to the 19th century when the salt treaty with the British provided the first push factor out of Goa. Then came the pull factors of port towns and a life that was seaborne. By 1926, of the rougly 30,000 sailors registered by the Bombay shipping office, 10,000 were Goans, almost all employed as stewards. The other pull factor is that migration occured in tandem with Indian migration. Goan migration does not exist in isolation, it is always found to co-exist with Indian migration of Parsis, Kutch, Khojah and Baniya settlements.
The next great pull factor was the Arabian gulf migration. It is wrong to assume this was solely because of oil. There were Goan businesses in Muscat dating back to 1880.
Lastly came the new migrations of UK, USA, Australia and Canada. Each of these has a different history to it, which I'm now too lazy to type out by do check out East African displacement post-colonisation and the Portuguese passport.
Take care,
selma