Glacier thermal regime change

If you know so little about thermal properties of glacial ice covering large mountains then how can you construct accurate future and past global warming models?

Working at heights of up to 5,200 metres on the Khumbu Glacier, the research team used a specially adapted car wash unit that produced a pressurised jet of hot water to drill boreholes as far as 190 metres into the glacial ice. Strings of temperature sensors were installed into these boreholes and left to collect data for several months.

Dr Quincey said: Until now, the limited amount of data collected from glaciers in this region has made it difficult to predict how environmental change could affect the glaciers' internal dynamics.
'Warm' ice in world's highest glacier

Proposed Sea level rises are mainly due to melting of glacial related ices and icebergs?

Khumbu Glacier borehole thermometry

Knowledge of glacier thermal regime is essential for predicting dynamic and geometric responses to mass balance change and determining subsurface drainage pathways, which ultimately influence proglacial discharge and hence downstream water availability. Yet, deep internal ice temperatures of these glaciers are unknown, making projections of their future response to climate change highly uncertain ...

We show that the lower part of the ablation area of Khumbu Glacier, a high-elevation debris-covered glacier in Nepal, may contain ~56% temperate ice, with much of the colder shallow ice near to the melting-point temperature (within 0.8 °C). From boreholes drilled in the glacier’s ablation area, we measured a minimum ice temperature of −3.3 °C, and even the coldest ice we measured was 2 °C warmer than the mean annual air temperature
Polythermal structure of a Himalayan debris-covered glacier revealed by borehole thermometry

These climate changing models seem to mention chemical and thermal heat sinks, rely on them? Combined with the greenhouse gas models of the original greenhouse planet Venus being incorrect there might be a slight doubt on all these constructs of a warming and cooling planet in the past, present and future?