short-term wellness is normally smaller than long-term wellness. If we are ought to maximize outcome, we should avoid long-term disaster. Thus, it would be wrong to use geo-engineering and solve the short-term crisis. The potential future disaster outweights it.
If we say that future outcomes outweights current probem, we would be valueing future generations over current generation. Thus, by making current generation suffer to ensure the well-being of future generation we are using current people as tools to serve the future generation.