That’s ridiculous. The gulf stream accounts for about 4 degrees Celsius of warmth where it makes the greatest difference, which is the Western coast of the British Isles. That’s not even enough to bump back the urban heat island effect. And any change in temperature from such shifts would be compensated for elsewhere.
NO, not ridiculous. The cold deep currents and the upper warm currents have a definite effect on weather patterns. During the last ice age they know that the warm currents were diverted further south which affected the weather and rain patterns worldwide. That along with the slight difference in the earth’s angle to the sun caused dramatic cooling effects in the northern hemisphere. It’s not global warming, just a recurring earth cycle.