Dozens of behemoth cargo ships adorned with tall stacks of brightly colored containers still dot the coastline off southern California. Part of a shipping bottleneck plaguing US ports, the ships – their diesel-fueled engines always ablaze – are also pumping out pollutants as they idle, anchored off-shore. The clogged supply chain has been described as an economic calamity as the delayed cargo caused shortages in common goods and drove consumer prices higher. But environmentalists and public health advocates are concerned it’s also turning into a climate catastrophe.nnThe container ships awaiting entry are compounding the levels of contaminants that have long come from the ports and that impact the local environment, coastal communities and ambitious carbon targets needed to curb the worst effects of climate change. With the holiday shopping frenzy just around the corner, there are now concerns the problem may get worse before it gets better.nn“The conversation right now is really focused on supply chain backlog and refilling the shelves with products – but that’s not the whole story,” said Madeline Rose, the climate campaign director for Pacific Environment, a climate advocacy organization that has been pushing for retailers to switch to clean energy shipping.