The graph below shows three projections for future carbon dioxide (CO2) levels. - The "business as usual" line shows CO2 levels is emissions remain at current levels.
- The "constant 1990 emissions" line shows CO2 levels is emissions are cut to half of the level that they were in 1990.
Which statement is supported by the graph?
1) Climate change will result in the melting of polar ice caps.
2) The increase in carbon dioxide levels will cause a decrease in global average temperature.
3) Human activities have no effect on atmospheric carbon dioxide levels.
4) Future generations can be affected by the choices of current generations.