I am a lay man - neither botanist, nor a global warming specialist.
I understand that
1. Global warming is caused by Carbon dioxide in atmosphere
2. Plants fix Carbon dioxide - and more plants, less global warming
3. Plants can grow more (and more plants can grow) if soil has
Nitrogen
4. Some plants can have symbiotic relations with Nitrogen fixing
bacteria
5. But grass family does not have such relationship
6. Grass family is botanically most successful colonizer of land
7. Using genetic engineering we can modify organism behaviors
8. Bacteria are easier/cheaper to experiment than plants

Now, if we can alter behavior of some type of the Nitrogen fixing
bacteria and make them symbiotic with grass (wheat, rice, corn,
millet, sorghum, sugarcane, bamboo)
1. A lot of Nitrogen gets fixed into soil
2. Soil becomes very plant friendly
3. That should kick up plant growth
4. That should kick up Carbon dioxide fixation
5. That should bring down global warming

Environment impact could be less than altering plant behavior to
become symbiotic with bacteria.

At the end we get a percent or two nitrogen less in the air, better
soil, thicker vegetation and cooler planet - with slump in fertilizer
stocks - all for cheaper than many options for fighting global
warming. Not a bad deal!

Is anyone working in this direction?
-Bhushit