The answer to the question is 1 and 2 only, which means that if the global temperature increases beyond 3 degree Celsius above the pre-industrial level, the possible impacts on the world are terrestrial biosphere tending toward a net carbon source and widespread coral mortality occurring.

1. Terrestrial biosphere tends toward a net carbon source: This means that the natural carbon sinks, such as forests, oceans, and soils, which absorb carbon dioxide from the atmosphere, will start releasing more carbon dioxide than they absorb. This will lead to an increase in the concentration of carbon dioxide in the atmosphere, exacerbating the greenhouse effect and resulting in further warming of the planet.

2. Widespread coral mortality will occur: Coral reefs are highly sensitive to changes in water temperature, and a temperature increase of 3 degrees Celsius or more could lead to widespread coral bleaching and mortality. Coral reefs provide habitat and food for numerous marine species, and their loss would have a significant impact on marine biodiversity and the livelihoods of millions of people who depend on the oceans for food and income.

3. All the global wetlands will permanently disappear: This statement is not accurate. Although wetlands are highly vulnerable to climate change, not all of them will disappear if the global temperature increases beyond 3 degrees Celsius. However, many wetlands will experience significant changes in their hydrology, vegetation, and biodiversity, which could have adverse effects on the services they provide, such as water purification, flood control, and carbon sequestration.

4. Cultivation of cereals will not be possible anywhere in the world: This statement is not accurate. Although climate change will have significant impacts on agriculture, it is unlikely to make the cultivation of cereals impossible worldwide. However, it will lead to changes in the distribution, productivity, and quality of crops, which could have adverse effects on food security and human well-being.