Heat oil and saute onions until translucent, about 5 minutes. Add garlic, jalapeno peppers, carrots and turnips and saute until onion is tender. Stir in cumin and coriander and cook, stirring briefly for 2 minutes.
Add water and bring to a simmer. Cover and reduce heat to low. Simmer 20 to 30 minutes, until veggies are tender. Stir in barley and beans and bring back to a simmer. Cook about 10 minutes, until soup lightly thickens. Add lemon juice to taste.
In small bowl, whisk miso and a ladle of soup broth to make a smooth paste; add to soup. Stir in cilantro, reserving some for garnish.