Before that, we need to know what causes climate change. One of the main reasons are the carbon dioxide released into the atmosphere, it traps heat but allow more heat to enter the earth, therefore climate increases over the years.
1. Set air conditioner to a higher temperature (eg. 25°C) or turn on fans instead. Operating AC can use a lot of energy, and these energy is produced by burning if fossil fuels which releases carbon dioxide.
2. Take public transports instead of cars. The more private cars there are, the more pollutants it release, these pollutants includes carbon dioxide.
3. Turn off all the lights / electrical appliances when we leave a place. Again, electrical appliances require energy which is produced by burning of fossil fuels that gives out carbon dioxide.
4. Recycle and reuse paper that is only used on one side. Papers are extracted from trees and one main function of trees is to absorb carbon dioxide from the air. If many trees are cut, the amount of carbon dioxide in air would increase.
5. Do the laundry only if you have clothes full for the machine. If the washing machine is not full and you're starting it up, it really uses a lot of energy and water, which all again it triggers the release of carbon dioxide.
The water gets cold because the ice cube is endothermic. Which means it takes in heat. It takes the warmth from the water and melts the ice cube which the ice cube releases coldness which cools down the water.