I recommend googling "geoengineering global warming" and reading some of the top hits. There are numerous proposals for reducing or reversing global warming which are astoundingly less expensive than reducing carbon dioxide emissions, and also much more likely to be effective.

To your direct question about storing more water on land, this would be a geoengineering project. Some straightforward approaches to doing it:

Use rainfall as your "pump" in order to save having to build massive energy using water pumps. Without any effort on our part, nature natually lifts water a km or more above sea level and then drops it, much of it dropped onto land. That water generally is funneled back to the ocean in rivers. With just the constructino of walls, some rivers might be prevented from draining into the ocean. Large areas would be flooded by the river, storing water other than in the ocean.

Use gravity as your pump. THere are many large locations on earth than are below sea level. Aquifers that took no net energy to do pumping could be built that would essentially gravity-feed ocean water into these areas. These areas can be hundreds of meters below sea level, so if even 1% of the earth's surface is 100 m below sea level, then the ocean's could be lowered by a bit more than 1 m by filling these depressions with ocean water.

Of course either one of these approaches will cause massive other changes, although probably in a positive direction as far as climate is concerned. More water surface on the planet should mean more evaporation of water which reates more clouds which reflects more energy from the sun, lowering the heating of the earth. But of course a non-trivial analysis might yield a rich detail of effects worth pondering.

In the past features like the Salton sea and the Dead sea have been filled by fresh-water rivers, essentially meaning that rain was used as the pump to fill them. The demand for fresh water has stopped these features from being filled. It seems to me that an aquifer to refill these features with salt water from the ocean would be relatively benign in impact, since in nature these features have been fuller of salt water in the past, and so the impact of that water might be blessed by humanity as "natural" instead of cursed by humanity as "man made."