You missed an important part 
Carbon Monoxide is a green house gas. That Triarian action just increased the planet temperature, thus putting into motion a cycle that would result in the world boiling over. With the tempreture increase, more water will evaporate, resulting in releasing co2, which raises the temperature meaning more evaporation etc
Those seeds aren't fixing this, considering they don't seem to be removing the CO in anyway, just pumping out spores into an increasingly inhospitable environment. Given the gradual heat increase (and non gradual, since the energy projectors produce immense heat), the gas released by the walker might not be stable, as the particles have more energy.