Hydrogen atoms are compressed
together by the enormous gravitational force
of the sun, causing them to fuse int a helium atom (which is heavier than
hydrogen), subatomic particles and enormous
release of atomic energy. The attached
picture shows the sequence of the main reaction
at the core of the sun. 
 
        
             
        
        
        
That is a chemical change or reaction.
        
                    
             
        
        
        
One potential result of climate change is greenhouse effect that is defined as the accumulation of carbon dioxide in the atmosphere that retains heat radiated from the sun. While this can seem beneficial because plants use carbon dioxide in photosynthesis, elevated levels of carbon dioxide actually inhibit photosynthetic mechanisms (Xu, 2015).
        
             
        
        
        
C; to stop pathogens with light harming the host cell