Proven– we are losing 148 Gt/yr from ice melt. Mostly from the two polar ice caps. 10 years of such losses would make more than 1.8m depth if all the melt water was spread over the land area of NSW.
The paper in Nature is based on the Grace satelites that measure changes in the mass of the Earth’s surface and provides new evidence that West Antarctica is shedding ice mass.
Half the sea level rise noted this last ten years has come from melting land ice. The remainder is mostly from the increase in temperature of the oceans with some from other minor sources.
The ocean absorbs the majority of the additional heat trapped in our atmosphere. If all that heat remained in the atmosphere it would be very difficult to live on this planet as the temperature would vary much more than it does under the normal influence of variations in solar input, volcanoes, etc. The ocean acts as a massive absorber to moderate the climate.
Unfortunately, once the ocean warms enough, we create huge inertia for change with increased energy in the system. Such increased warmth will impact on all coastal regions. For example, the coasts of Antarctica will be washed with warmer waters that will drive ongoing melting of the ice caps. Warmer waters in the Arctic Ocean will melt permafrost around Siberia and northern Canada leading to release of further greenhouse gases CO2 and Methane.
Once begun, these processes will not stop until we return the planets energy balance to pre-holocene levels. If fact it is extremely difficult to envisage the human race being able to achieve such re-balancing at all. So we face changes that will be out of our control and continuing for centuries or millenia into the future.
It has for some time been critical for the planets future for us to urgently and on an emergency basis eliminate our use of fossil fuels. The remaining stocks of fossil energy must be left in the ground.