In the Farenheit scale, how much is an increase of 1-2 degrees Celsius?

Each Celsius degree is 1.8 times larger than a Fahrenheit degree, so just multiply 1-2 by 1.8, and that gives a range of 1.8 to 3.6 Fahrenheit degrees.

[Note that you are converting a temperature CHANGE, and not a TEMPERATURE, so you don't need to use the more complicated formula T(F) = 1.8*T(C)+ 32. That's because when calculating a temperature change the constant 32 will drop out when the difference is taken]

An increase of 1-2 degrees Celsius = 9/5°F = 1.8°F

F° = (C° x 9/5) +32

F = (1 x 1.8) + 32 = 1.8 + 32 = 33.8F.

so 1 degree Celsius = 33.8F. 2 degrees are 35.6F