In the year 2100 a global mean temperature increase of 2 degrees C, and a 50 cm rise in sea level are expected. An escalation in the intensity and duration of heat waves will increase mortality, whilst higher temperatures in cold regions may reduce it. On a global scale, vector-borne diseases such as malaria, dengue, yellow fever and some types of viral encephalitis are likely to increase. 50 to 80 million more cases of malaria could occur annually. Elevated temperatures and more frequent floods could cause an increase in salmonellosis, cholera and giardiasis. Indirectly, shortages of freshwater and foods may cause serious health problems. The world may see more environmental refugees. For Norway a temperature increase of 3-4 degrees C during winter and 2 degrees C in summer is expected, with more precipitation, especially in western parts. The possibility of the Gulf Stream turning at 40 degrees N and causing a temperature decrease of 10 degrees C, is not very likely. Malaria could reestablish itself in Europe, but hardly in Norway. The most harmful arthropod vector in Norway, the tick Ixodes ricinus, might extend its range into the most populated parts of the country. Marine algal blooms might increase the risk of cholera. Health problems caused by greater floods, poisonous algae and certain freshwater cercaria might increase.