The main concern is the effect of extra heat on local climates right now. It is possible to imagine increasingly anomalous weather and increasing loss of life and property from greenhouse gas accumulation with very small changes in the average temperature of the planet. You can increase the temperature in some areas and decrease in others and you can alternate - the differential effect will drive storms and precipitation in unusual ways. Increased adverse weather events can be best explained as an exaggerated differential effect. We built a greenhouse with gases over much of the Pacific Ocean and put up heat shields in other areas - smoke, other particles and water vapor.
Weather extremes are commonplace and loss of life and property from adverse weather is increased.
There is no need to wait until 2050 to find out what is going to happen. Ecosystems are precariously balanced around temperature, pH, oxygen and carbon dioxide concentrations. The negative consequences of our actions may escalate beyond our control. The predictions of climate changes that might occur because of more greenhouse gases are coming true - not fully and completely, but convincingly. There is cause for general concern.